I have personally only camped at the beach once. We went up near Big Sur. There was a lot of poison ivy and the only useable beach was 4 miles away with a huge trek down the cliffs to the beach. So, another place would be better.
But we have camped often with our now 2 and 3 year olds. Definitely bring more supplies than needed. Tons of diapers, wipes(lots of them) and the usual diapering necessities. And extra cloths. If you don't use them... at least you had them just in case. Bring warm stuff for the evening and night. If you're near the beach you must remember that it is damper. We camped in the Sierras and made sure that the kids had long-sleeved onesies under their cold-weather sleepers. We also put hats on their heads and gloves on their hands. Check what the weather will be like in the evenings to know how much to put on your wee one.
Bring sunblock and bug spray (look for both for kids). At the beach, you shouldn't have problems before dark with mosquitos if at all. But, always be prepared. Up in the mountains, we definitely had to use both. Very important --always make sure that sunscreen is put on before the bug spray if you do need both. Otherwise, you're covering up the stuff you need to keep the bugs away. If you're going hiking or on long walks, bring a pack for carrying your little one. Even if they are walking now, they can't walk as long as we can.
Check if the camp sites have grills or pits onsite. If not, you'll need to bring your own. Bring wood to burn in the pits if that's what you're going to use. It's better to cook on than coals and less smelly too. Bring a lot of finger foods, snacks, and such that will keep without fridge. Bring lots of water. (Check and see if your site has potable - drinkable - water. Nonpotable is not for drinking.)
As for sleeping... may I suggest the PeaPod. It is a cool covered sleeping tent that confines and protects. It has an inflatable mattress that inserts under it and the tent keeps the bugs off. We used this outside as well at nap time and sleep time when we were still outside and wanted them with us. It takes up little space when closed and sets up easy. We always just throw it down away from us and it pops up all by itself. check ou the site... http://www.kidco.com/main.taf?p=4,5.
Bring toys that you won't have to worry about getting dirty or lost. You know what your child likes to play with. We brought stuff we know would keep them busy when we wanted to lay back. We brought a bouncer chair with toys that hung from it when they were very small. Don't forget the sand toys. Some people bring play pens. We didn't because it would take too much room. And... we were camping and expected that everyone would get filthy. This is where wipes comes in handy as well as washcloths with water. (nonpotable is okay for this)
The most important tip that I have for you is.... ENJOY YOURSELF and take LOTS of pictures!!!
