Thanks for the replies everyone,
We're going camping on Padre Island National Seashore, right on the beach. Six people when we're all there, and about six nights total. Camping on the beach requires copious amount of sunscreen and bug spray... kinda yucky when crawling into bed without washing.
Sounds like 5 gal buckets is the way to go. Easy to pour into the camper tank, and I can fill them with gray water and dump everything on the way out. Black water shouldn't get full... you don't have to use it so long as you bury your waste.
Thanks!
s10texan