FastPass/dinner reservation planning with park hoppers... Help!

So I know we can reserve FastPasses ahead of time, but I just changed our 3 day "regular" park tickets to 4 day park HOPPERS. My question is: How soon do they announce how late each park will be open, and how do you go about planning FastPasses with park hoppers when you aren't sure where you'll be each day/night or would like more flexibility. Obviously, I don't want to make them too early or too late, but then am I committing myself to certain parks and not allowing us the freedom to go where we please when we please? (We want to be at the parks that are open later on the nights they are open later, etc.) I guess this applies to dining also, and I will have to completely redo our dining plans... We would like to spend some time in the parks from when they open until about noon/1. Then go to hotel for a 3 or 4 hour break, then head back out. I assume it takes quite a bit of time to hop between parks? Any and all advice/information on planning dinners and FastPasses when park hopping is welcome. :)