We have taken my 5 year old 5 times and my 3.5 year old 4 times. Both were there around 2.5.
Festival of Fantasy parade was a HUGE hit for both my kids at this age.
For dining, we personally prefer to just book a couple TS meals ahead of time and do mostly QS or book last minute TS. While my kids do great in sit down restaurants, I don’t really like to be on an eating schedule with them at WDW. For example, if they’re acting hungry at 4:30, I don’t want to give them a snack if we have a 5:30 ADR, etc. I’d rather just get an early QS dinner with lower crowds and a fun treat later. We also like to book TS on the go and often find great last minute options (even for our group of 8-12 people.)
Will he stroller nap? Mine did when they were younger and still did at 2.5. If we went back to the hotel for a “rest” at that age, it was not very restful

They’d just get amped up when we got back to the hotel. My oldest stopped stroller napping around 3.5. My youngest who is 3.5 now still took some catnaps in the stroller on our trip a month ago. All kids are different in this department, but mine would never nap in the room. On the go worked best for us.
2.5 is a very fun age at WDW (or at least was with both my kids!)