I think an early wedding sounds fabulous! I know they do ceremonies at 12, you'd have to ask for earlier. The lunch reception, you can probably go super casual and low key and ask for part of the buffet to be reserved for you. Then lots of kids choices for meals and nothing too formal or stuffy.
For a group with a lot of kids, I recommend staying in Coba. They have family suites and a children's waterpark. You can then still have your ceremony wherever you'd like.
The BBQ private reception is amazing and delicious, but I'm pretty certain that can only be done at night after the normal crowds have died down.
With a symbolic it should not be a problem at all to have your friend marry you.
Best wishes and it sounds like you're going to have an amazing time!