As far as Camp Carnival..we didn't use it. It looked like they had alot of great activities. You don't sign up ahead of the cruise but I think you HAD to attend the orientation the first night and we missed it. I didn't bother trying to get my 5yr old in late b/c we were only on a 3 night and we were busy enough. We aren't partiers so that was ok. We also had a 15 and 12 yr old that would stay in the cabin with her when she was sleeping so we could go to the late comedy shows. It worked out well for us.
For dinner you have the option of eating in the casual dining buffet area or eating formally. You should have been asked when you booked what setting time you wanted. You are expected to use that seating if you eat formally but if you chose not to show up and go to the buffet you don't have to notify anyone. Your seat is there if you want it. All other meals are open seating. There is no meal tracking..if you see it eat it. (except for this really cool specialty dessert section in the Galleria. It costs extra. You get dessert with your regular meal but these are like special special truffles and stuff.
As far as showing up they TOLD us 1:30 so we did and it was fine..not a bad wait. BUT someone here had told me you could go as early asa 11:30 and I forgot. After we got on the ship I realized we would have gotten a little more time on ship...more pool time the first day... and we would have gotten to do the ship tour had we gotten there early. So if you can go earlier...Lifeboat talks for us were at 4:00 and I think we left at like 4:30 or 5:00 ..it was pouring rain when we left so there was no grand sendoff like you se in the movies... I don't know if it was the rains fault or if that;s just in the movies...
(this was our first cruise too so take others advice over mine