We love getting there early enough to go to a park for part of the day on arrival day. We call it a bonus day. We just plan on enjoying the park atmosphere and any rides or characters we get in are a bonus. Although I despise FP+, I have to admit it is pretty useful for that half day on arrival day because you can schedule headliners in the evening. Which park depends on the park hours and season. In February, the season doesn't matter too much (i.e. for Christmas we might do dinner at DHS and Osborne lights- I'm gonna miss those light). I would go for the park with the longest hours, which typically is MK, unless you want to save your child's first MK experience for a full day in the morning. We have done EPCOT and that is great to have a nice dinner and then a ride or two and some atmosphere, but with the ADR cancellation policy, if you are flying that is taking a risk. If your flight gets delayed and you miss your ADR, WDW might waive the no show fee, or they might not. We did that with DD when she was a preschooler and we would stay until fireworks the first night, and even with the plane ride and park until late, she never had a problem getting up the next morning ready to go (she is a high energy kid though).
