It Is Still Impressive!
There is some general information that is relevant to this area... not quite right for any particular hike, but very nice to know as you tour the area.
The number one question/mystery: where are the active lava flows?! Well, the Halema'uma'u Crater down in the bottom of the Kilauea Caldera is still boiling and belching, but... you cannot go there anymore. You can view the site after sunset from the Observatory area, with the orange glow illuminating the off gassed steam.
There is active lava... way on the ocean side, east end of the park. There are commercial boat tours that will get you to those areas. You could hike along the coast... no trail... over hardened lava! 15 miles off trail!
You will hear about a road that gets you there, it does not. It takes you to the area that was devastated over the last thirty years, with the last homeowner being lifted out by helicopter in 2012. Alas, this is all private property. You will drive down and find local police making sure you do not venture out to find the real flow. Of course, the status of outflows is constantly changing... you might get lucky!
Camping/Housing: Overnight backpacking is allowed, by permit, on the outlying trails throughout the park. The Volcano House is currently under remodeling; that was the lodge in the park boundaries. Across Hiway 11 from the park entrance is the Kilauea State Park that may accommodate camping. The nice housing comes from the local B/B's... Private lodges... and the Volcano Inn system of units (extremely nice units, complete with hot tubs surrounded by giant fern trees!)
Food: Okay... Hawaii eating can be really expensive. At the stores, count on paying twice what you'd pay stateside. But... time it right, hit the local Farmers Markets and score x10 papayas for one dollar! The variety and prices are impressive at these local events. Hilo has a Saturday and Wednesday market... worth the drive even if you are staying in Volcano. Additionally, there are some larger stores, not cheap, but cheaper than the small stores in Volcano. If you are coming from the Kona area, take the time to stock up at Costco... stateside prices!
Fire Season: Even with all the rain, they seem to enforce seasonal closures of certain roads, including the main route up Mauna Loa. Check with the Rangers to determine if your trip will be impacted.
Crowds: I'm not sure why, but this park attracts huge groups. They do not appear to be hikers. They flood the Visitor Center and the attractions immediately along the road sections that are open. The one exception is the Kilauea Iki Crater area with the Thurston Lava Tube. Unfortunately, the IKI is exceptional, so to avoid the crowds, go early. There could be hundreds of folks walking that loop.
Hilina Pali Overlook: looks good on the map, but really this is just a nice kickoff point for a variety of looping day hikes or extended backpacks. It is narrow and rough. If you need to log some more car miles, drop down the Chain of Craters road to the Petroglyphs... or all the way to the ocean.
Plan your trip carefully, with an idea of just how many days you want to vest in this most unique hiking area. Also, consider flying into Hilo and biking or busing out to Volcano. Car rentals can be expensive here. You could walk over to Walmart, buy a $100 bike and enjoy a very intimate bit of touring. If you are going to stay in Volcano, or be backpacking, you could consider doing without a car!
Check out the Triplogs.