I don't think your being too precious. I think it's quite natural to have a little worry or concern.
I've just been to florida with 5 other adults and 3 children. My dps parents took along their 2 gc and we had my dd. There is no way we could have done a park every day, the heat, the crowds, the soles of my feet screaming. We also 'shared' out the responsibility of looking after the children and I have to admit I was so glad we had other adults to help. No matter how fit you are, 3 children to watch over, push luggage for through a busy airport, plaster in sunscreen(sometimes several times a day if they're in water), feed, entertain, corral, please, get on rides suitable for their age and look after the others who are too young or old for the particular ride, take shopping and keep safe is a daunting task.
However, being prepared for all of the above, planning and a few rules set down before leaving, it could be done.
I'd suggest staying in a house rather than a hotel. There are some lovely vacation homes for rent with pools and all the home comforts and actually all three of our juniors preferred the pool to all other costly entertainment which of course we didn't mind as it gave us a chance to relax 'at home'.
If you would like to go but are worried about money, a rented villa could help reduce the cost so consider it before writing it off. The rental cost split is far cheaper than hotel rooms, you can cook your own food so less cost on eating out(walmart and publix are cheap and have everything under the sun you could need for a holiday) We brought one bag each away with us, bought all our holiday clothes, sunscreens and pool toys for next or nothing over there and bought another two bags for half the price you'd get them at home for bringing all our new stuff back. You spend more time at the house, BBQ, pool, safe, private haven so less expensive days than a themepark everyday. There are loads of ways to bring down what initially seems like a huge financial layout, really worth considering and of course you'd get to be part of those lovely memories too.
Hope it all works out whatever you decide.