I don't think it really matters what park you do on which day - but I do think making a plan before you go is a good idea - it gives you an idea of what tickets you will need, and also means that you know you will see everything, so you don't have to worry about 'what are we going to do today' each morning - or panicking that you haven't been to Epcot yet, and when will we get the chance - you can just look at your plan, and see that Epcot is on Thursday, so we can enjoy MGM today secure in the knowledge that Epcot is coming
Bev