I'm assuming you haven't been there before. Or at least not since you had the kids.
Wow! This is an expensive way to do a trip! Sounds like you're paying for US and SW separately. You can actually get a pass that will let you into US, IOA and SW -- that would easily take up 3 days. Or you could do SW for 2 days (the 2nd day is free) and 1 other park for 1 day) Or you could even have done all 3 days at US and IOA for just $99 per person. Or you could save money for each additional day you spend at WDW.
I would suggest you rethink this plan, especially since 3 days in a row at different parks can be exhausting.
Or if you still want to do all 3, get the 2 park pass for IOA and US (personally, I would just choose 1 and save the other for a separate trip). I would suggest that you do MK last, since your DD8 will want to go there every day after she sees it -- if you go there first, it could make the rest of the trip not so fun with her asking to go back every day.