We stayed in site A42 for 10 nights in mid May and it was a great experience. We are full-time, have a 40' Class A motorhome, flat tow a Jeep, have 2 kids, and have 2 dogs. The site itself was wonderful. It was a large pull thru, nice & level and had plenty of comfortable space between it and the neighboring sites. It had a nice concrete patio, beautiful built-in fire ring, and and great solid patio furniture. We didn't even have to bring out any of our outdoor rugs or furniture.
As for the location, it was ideal! It took maybe 15-20 minutes to get to the falls. There were great eating options in Niagara (15 minutes out) and even right outside of the campground at Adrian's Custard & Beef. There is a grocery on Grand Island as well that takes 5 minutes to get to. Wal-Mart and all other stores you could need are within 15-20 minutes.
The kids loved it too! There is a nice playground, fishing, bikes to rent, a jump pad, basketball goal, arcade, and a pool for summer. There is also a place next door for go karts, arcade, and mini golf.
We explored the area quite a bit and this is by far the best campground on the US side to see the falls. Would definitely recommend.