We camped last May at Buffalo Point campground, here's a link... Campground Details - BUFFALO POINT, AR - ReserveAmerica - [NRSO]
. It was quite a nice campground. It was almost 100% full in mid May on the weekends.
I kayaked that part of the Buffalo River, but in mid May, the water levels were very low and had to do some walking, particularly upstream. I understand that the water levels are high in the spring and fall. If you google 'Buffalo National River' you'll find sites that monitor water level.
I have lots of pictures from that trip in the member's photo gallery if you're interested.