Hi Lori,
Thanks for visiting us at the Disney Parks Moms Panel with your great question! So the short answer is that no, you don't need to plan which park you want to attend each day ahead of time, but there are definite benefits for doing so. You're exactly right that
dining reservations play into it and will determine which park you may enter each day if you plan to dine inside a theme park. The other main benefit to planning ahead, though, is that you are able to make
FastPass+ selections 60 days before your arrival if you're staying at a Disney Resort hotel, and 30 days prior if you're staying elsewhere. FastPass+ is a wonderful and complimentary service that helps you save a ton of time by bypassing standby lines, so I'd definitely recommend making up to three selections per day before you even arrive for your vacation. You'll need to select one park per day to do so, though. If you don't wish to plan ahead, you are certainly welcome to choose whichever park you'd like to visit each day once you arrive for your vacation.
And to answer your question about stroller rental, once you arrive you'll have the option of
renting your stroller for one day or for the length of your stay. The cost does go down a bit per day for a length of stay rental, so there is an advantage to that option. Either way, strollers do need to be returned before you leave the park each day. If you purchase a length of stay rental, you'll simply show your receipt to the Cast Member at the stroller rental location each morning, grab a new stroller, and get started on another wonderful day!
Please let us know if you have any other questions, Lori, and have a truly magical vacation!
Missy