I totally get it. I was a spreadsheet planner who loved FP+ because I could tour efficiently and clear half the park by lunch.
Now sometimes I don't even get to a park until well after opening and I go to Starbucks and wander around for half an hour before ever getting in line for a ride. I go solo quite a bit (heading down there Monday!), so that ramps up the freedom even more. But when you're taking the family, the extra pressure of feeling like you're in charge of everyone's happiness can really drag you down. I learned to let go (mostly, LOL!!) and allow for more spontaneous fun. But that did not come easily to me!! I still get caught up in it sometimes.
My kids are 17 and 19 and the only thing they knew they wanted to do was eat at a couple of specific restaurants. Most days they slept in and met up with us later. Usually for the aforementioned food, LOL!!
While I long for the days of no park reservations and park hopping at any time (this one hurts the most for me!!), we have adjusted to it and found ways to make it work for us.
If you aren't able to change park reservations, you do technically have to go tap into your reserved park before heading to the new one, but you should be able to rearrange things if they decide to roll up after you've already park hopped.
Unless you're annoyed with your kids, and then you can just make them go ahead and go to the first park for revenge
Going with my kids now is great because I still get that special time with them, but I also get special time WITHOUT them. My husband and I have so much fun hanging out and just enjoying being together at our favorite place, and then at dinner we can all gather back together and talk about our day. It spreads the magic around a little more.
I really do hope you have an amazing time!!