Camped many times on Ark (Numbers & Browns Canyon) for guys trips. Are you talking camping at campsite then doing multiple day runs or talking overnight off the kayak/raft with all gear (including firepan, toilet, etc.?) We generally camp/drink at one of the Ark Headwaters Campsites (with boat ramps) then do multiple runs down Browns and other stretches straight from or to campsite. We're going in June (Ruby Mountain) for just that. Best campsites are Hecla Junction, Ruby Mountain and Railroad Bridge for large groups.
There are some other cool unimproved riverside campsites, most on side of road off Numbers stretch. Brown's is only stretch not by road, busy with commercial groups, and does have a few "wilderness" campsites for river-access only that you would come across. Hope that helps...
Camping at AHRA | Colorado State Parks