I stayed at Watchman campground when I was there in 2007....I am NOT a campground person! It was too busy and too noisy. We had our fair share of "party people" who were up half the night (keeping our whole section up as well) and then what campground wouldn't be complete without the "midnight arrivals"? Banging their gear around, slamming their car doors every time they retrieved one item and had their propane lantern so bright, I thought it might be a solar flare!
I'd recommend a hotel or cabin in Springdale and there are shuttles that leave from there at regular intervals.
Have a great trip!
"May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view. May your mountains rise into and above the clouds" Ed Abbey