Congratulations on getting into physical shape for your Canyon trip (lose a few pounds for me). You are planning an extreme hike for a first-time Canyon trip. If I recall correctly, you are going down the SK, one-or-two nights at Phantom, up the NK to stay at the lodge, down the NK and another night at Phantom, back to the South Rim via the Bright Angel. This is a Rim-2-Rim-2-Rim (R2R2R) hike and will cover 50+ miles.(I checked on your orginal agenda: "My question is this - for a 6 day hike - Down SK, PR for 1 nite - up NK - stay there for 3 nites with a bunch of hikes down and back while there and then down NK and up BA - what kind of footware would you recommend.") That is an advanced agenda for even experienced Canyon hikers. From your description, I'm not certain if you are camping each night OR are you going to stay at Phantom and the North Rim lodge? I'm going to guess that you are staying at the lodging accomodations and have not pulled a camping permit----the Backcountry office would most likely challenge your plan based on your first time hike. You have some long days in there----from Phantom to the North Rim is about 14 miles (add another mile if you can't hitch a ride to the lodge) with about a mile in elevation change. In mid-May, there will be about 13-14 hours of daylight with light muted within the Inner Canyon much sooner. There is a good chance that attempting that uphill hike in one stretch is going to have you approaching the North Rim after dark (based on 1 mile per hour) with cool-to-cold weather conditions. Once you hit the trailhead, you still have about a mile walk to get to the North Rim Lodge.
Of bigger concern is the conditioning of your hiking partner. If he got gassed on Bear Mtn in Sedona, he'll struggle with the 50 miles in the Canyon. The Bear Mtn. hike is a 5 mile loop with an elevation change of 1800 feet. If you wish to use Bear Mtn. as your calibration point, you would have to do that loop three times in a single day to approach the same conditions you are proposing with your Phantom Ranch to the North Rim hike. That is still only 15 miles out of the proposed 50---in other words, both you and your partner will need the conditioning to handle Bear Mtn. 10 times in 4 days.
Even if you are in great physical shape, you are only going to go as far as your hiking partner----unless you want to abandon him on the trail in order to get to that dinner reservation! We'll look for him on "I Shouldn't be Alive.' A good first hike is to go down the SK, spend a night at the river, then back up the BA. This hike introduces you to several of the more common Inner Canyon sites. This is app. 17 miles. Once you and your partner get calibrated to the Canyon via this hike, then you can start planning those longer adventures. http://www.nps.gov/grca/planyourvisit/u ... ochure.pdf
The next longer option is to do a R2R by taking the TransCanyon Shuttle to the North Rim, spend the night, hike down the 14 miles of the NK to the River, spend the night at Phantom Ranch, then back up either the SK (no water along the trail!) or up the BA. During the hot months, the recommendation is to break up the NK to the River and spend a night camping at Cottonwood campground. In summer, the Inner Canyon is very hot and at lower section of the trail, known as 'The Box' is an oven.
The TransCanyon Shuttle costs $80 leaving the South Rim to the North Rim---you leave your vehicle parked in the Backcountry Office parking lot on the South Rim. http://www.trans-canyonshuttle.com/
If you want to continue with your current plans, be sure to have an 'ABORT' option already worked out between you and your partner. Make an agreement ahead of time if one person needs to ABORT, there is no debate. The 7.5 mile hike down the SK will do people in if they get blisters or overwork the leg muscles by lunging forward while hiking down. Know the early warning signs for blister formation, take a 15 minute break app. every hour on the way down, stay aerobic to prevent lactic acid build-up and painful leg muscles. After the night at Phantom, make the ABORT decision---if you turn around, you have 9.5 miles via the Bright Angel or 7.5 via the SK (no water!). If you continue up the NK, you are both committing to an additional 40 miles and trying to get up the 15 miles to the North Rim before dark. The trail is well-traveled---but can be a challenge when you have never seen it and are gassed. If you are not going with full gear and self-contained---be alert to getting stuck out on the trail without warm clothing, etc.
You mention that you are going to stay on the North Rim for three days and do hikes from there. There is really only one Inner Canyon trail that is within walking distance and convenient to the lodge---the NK. The other Inner Canyon trailheads from the North Rim require transportation and time to reach. The orignial North Rim BA is accessible but is not maintained and not recommended for a first hike. The other hikes from the lodge are all Rim trails, great in summer when the Canyon is dangerously hot. If you have 6 days at the Canyon, you can stage some dayhikes from the South Rim that will give you plenty to do. Good dayhikes are to go down Hermit Rest trail over to Dripping Springs, down Grandview to Horsehoe Mesa, down the Tanner Trail to 'Stegasorus Rocks'---these trails are not maintained, and you will need to provide water for Grandview and Tanner and a method to treat water from either Santa Maria Springs or Dripping Springs along the Grandview.
If you spend the night at the North Rim, you still have the 'ABORT' option if the remaining R2R is going to be too severe. The TransCanyon shuttle driver spends the night at the North Rim and the shuttle leaves for the South Rim at 7 am---call ahead if you need a ride back to the South Rim. As Dschur has pointed out, May is a crazy month for R2R hikers and long-distance extreme runners anxious to get their 'Canyon Fix' by doing the hike/run when then Inner Canyon is still bearable. The shuttle bus back to the South Rim normally doesn't have the same passenger count since most hikers enter the Canyon via the NK, not exit via the NK.
Your first hike should be a satisfying adventure and not a death march. If you come up with a hike that allows you both to suceed, it will go a long way to bond your friendship. The reverse can also be true---if either one of you gets overwhelmed, it runs the risk or tainting or ruining a friendship. Once you get the Corridor trails under your backpacking belt, you'll both use that success and good experience and be gung-ho for the other trails and loop hikes---and a long love affair with the Canyon.