Jolly Roger (on Grassy Key just above Marathon.) Rates vary, might be about $80 but if you have Passport America membership, half price which makes it about $40. They are pretty full (we're there now).
We filled in a night last year at Jolly Roger and returned this year for a week. They keep improving it - new bathroom reno ths year. New pool last year. Dock out on the water is great for sunset viewing. Staff has always been friendly.
By the way, we stayed at Big Pine Key fishing lodge for a couple of nights last year. Could only get dry camping, and no generators permitted. No pets. Also about $40 so that could work if those issues don't matter.
