Hi Cari!
Dining reservations are one of the biggest hurdles, so you've crossed a big threshold securing those. If you are considering any other special tours and experiences, now is the time to secure those (you can access the Tours and Experiences link by clicking here).
Your itinerary is largely dictated by those places you have to be. Once those are set, you can figure out the rest of your planning. But again, those tours may cost money, so you want to make sure your reservation is secured before booking any of those.
I generally look at my planning three ways: Parks, Dining, Other (Shows, Activities, Miscellaneous). I then prioritize between "Must Do's" vs. "If We Can Fit In." Then I can plan according to that.
For our family, Magic Kingdom takes 2 days, while the other 3 can take 1 day if you start early enough. Take advantage of the Extra Magic Hours wherever and whenever possible.
Beyond that, relax, enjoy, and have a great time! :-)