Hi OP!!! I am taking both of my DD's (6 and 2) at the end of June also! Good luck to you, and I hope you will remember to come back and let us know how your trip goes!!!
Being that I havent done it yet, I cant say my advice is tried and true.... but in my head it makes sense! We will be doing table service! Keeping both kids with me, holding a tray full of food, and searching for a table... eek... then I can see it now, "mom i forgot...." or "mom i need ketchup..." so then we all three would have to get up and go get it. I think the extra $$ will be worth it for someone to do the serving!
And even though my DD6 can swim, and swims with out floats at home, on this trip, we've already taked and she knows she HAS to wear her puddle jumper at all times in the pool.
As far as strollers, I bought a Mclarin (sp?) double off of craigslist for next to nothing for our trip. I like the idea of a single and have them switch, but sure enough, they will both get tired at the same time. I am trying to prevent as much of the bickering as I can.
And either spring for the memory maker, or join a facebook group to find a share to cut the cost. My dd's love to meet characters, and i like knowing I will have plenty of great pics and not have to worry about my camera!!!
Im excited to read everyone elses tips and advice!