I think that it is tempting to try to get the biggest bang for your travel buck, but do you really want to rush that first day? If we had more info about your travel time, when you arrive, where you are staying and he length of stay, the advice could be more targeted towards your circumstance. But with that said, we never ever rush our first day, and looking back, when my DGD was 4 and we arrived on her first trip, that was teh best decision for our family. We got to AKL fairly early in he morning, checked in and had lunch, explored the resort and took DGD swimming, She rested, awe we headed to Chef Mickeys for our arrival dinner. SO Much FUN! She was mesmerized! Worth every Penney of no park time.
This trip we are taking two little girls on their first trip and we have Chef Mickey's planned again. I have fast passes booked for the MK that afternoon because I am afraid that if they can see that castle they will want to go for a little while. WE honestly do not care if all they do is absorb that they are there, and let them just explore.
So...if this trip you are planning was me, and I wanted park time that first day, I would get Crystal Palace for a late lunch. You do not need to rush to get there, you can let your DS explore, and after lunch, you can go back to your resort, swim rest, have a little dinner and early to bed. You do not want to be THAT family. You know the one.....all exhausted, irritable, and trying to get an overwhelmed and over stimulated little boy out of the Happiest Place on Earth before he melts.