Hello Kathryn!
Like you, I am always trying to figure out how to eke out the most amount of Disney Parks magic from every trip. While I'm a HUGE fan of coming in a "day early," I am not a huge fan of getting in late. In fact, the times when my family has arrived past 9:00 p.m., we tend to not go to a Park the next day for the whole day. Why? At least for my kids, the travel day can be tiring- so much excitement and anxiety. This coupled with a late night and waking up early to be at a Park before opening combines for a dangerous likelihood for meltdowns- and sometimes it is me melting down! If I could wave my magic wand for you and your family, I would have you arriving the day before your first park day by 7:00 p.m. Arriving early evening allows time for winding down, eating a quick bite, and exploring your resort before settling down for a good nights sleep. However, you know your family better than anyone else! If you think that they would do well with a late night and early morning combo, go for it!
However, if you don't want the added night to include the dining plan, you will need to book a separate reservation. If you book a separate night at the same resort, It may be possible to stay in the same room, but you will be required to go back to the front desk and check-in again. It is also possible that you will need to change rooms.
I noticed that you will be surprising your kids. Recently the Disney Parks Blog highlighted some great ways to surprise little ones with a trip. Even though it is entitled
"Big Surprises for Little Kids," the ideas will work for big kids too. Have fun planning your Disney adventure. If you have more questions, come on back to the Disney Parks Moms Panel. We love helping to make vacation dreams come true!
See ya real soon!
Anne