I would do a general plan at least every couple of days. I might tell them that during the time that it is not meal time they are welcome to do what they want within the confines of the allowed activities. I have not been there so don't know what is expected.
So, if I were inviting someone to join me at the local zoo and Omniplex, other museums, etc...I would plan the itinerary like this.
8am breakfast at XX for about 30 minutes, go in to the zoo complex. Get the stamps and other stuff so that all is taken care of and they won't be shut out of anything.
at noon we will meet at XX restaurant for lunch.
After lunch we are attending the Planetarium's light show, if you'd like to see it with us let me know so we can meet up outside.
at 3pm we will meet at XX for snacks
Then at 6pm we will meet for dinner.
This way they get to have some alone family time too. Other days you will have a much tighter schedule and be together every minute. That will get old if you expect them to want to do the same exact things that your family likes.
It will be a lot more fun if you only plan one or two activities together each day. It can also work out where you are going t the same places as each other all day but just having the freedom to say "Hey, I want to go check out XXX" then go is a wonderful feeling.
If there is an emergency then calling the other family on their cell is allowed and expected. I would enjoy a trip like this but would want to spend at least some time with my own family and not have responsibilities to attend some show I would not like.
I know I would thoroughly enjoy The Gilcrease museum but kiddo's would not enjoy more than a few minutes. I would want to go with hubby and leave the kiddo's to do some activity with the other kids. If there are activities that they don't want to attend why make them go? Let them do something during that time. If you would have paid $100 for them to go to Seaworld then perhaps handing them some cash and allowing them to choose to do something else would be fine.