As Phamton said, the express + passes will be pretty pricey. If you have 4 people, that is going to be $140.00 - and that is just for one park (adding the second park is additional). Have you checked into getting a room at the RPR for the night? It might be more cost efficient. Even if you never move into it with suitcases and such - you have a place to go to relax and can take an afternoon swim break. And the bonus is you get unlimited FOTL for the entire day** you check in to park closing of the day you check out. And you can use your room key at both parks anytime. Much better than spending all that money for only 1 time per ride as the Express Plus Pass limits you to.
Just checked online - an express + pass for either IOA or US is $37.28 in July. Don't know how much the 2 park pass is, but I believe I read somewhere that it is an additional $10 - $20 depending on the date.
Rack rate for the RPR is $234 for a standard view / 2 queen (you can probably do better if you have
AAA or find a discount).
So, if we do the math...
4x37.28 = 149.12. Say the second park is $15.00 per person - that is another 60.00 - total $209.12. For only $25.00 more you get unlimited FOTL for 2 days rather than 1 time per ride per park for one day.
And as Phamton said, July is very busy, so if you decide you want to ride something a second time, that 60 minute wait is going to seem much longer after you just stood in a 15 minute line
Just another option you can explore, especially if your family hates lines.
** If they implement the FOTL restrictions from last year - you will get 1x per ride before 3pm and unlimited for the 7 hours (3-10pm) after 3pm. Another great reason to have a room - during the hottest and most crowded part of the day - you can take a pool break!