So, I dropped the ball on my 11-year-old’s spring break and am now thinking a few nights in Merida (fly into Merida), then a few nights at a resort in Akumal (leave from Cancun). I think we will both enjoy a small city with good food and then some beach/cenotes time. The big question is: How many days in Merida and how many days at a resort? Is 3 nights in Merida enough? 4? We’d like a day to see Uxmal and/or Ek Balam. also, what are your favorite things to see and do in Merida (besides eat)? I am not looking for kiddie activities per se; I’m looking for things we will both enjoy. Thanks as always. Also! Your thoughts on why one should choose Uxmal over Ek Balam or versa?

Uxmal is closer to Merida but I did like it and the evening light show is worth seeing (although narrated in Spanish). I would look into 1 or 2 nights at a hotel in Uxmal (we stayed at the Uxmal Maya Resort). On the weekends they have a nice brunch spread. There would be an advantage in going as early as possible, and being able to take a mid day break.

Maybe also go see the flamingos near Celestún?

BBC - Travel - Relaxing among the Yucatan's flamingos

Do you have the Moon Guide? It's excellent for the area.

Uxmal and the Ruta Puuc are magnificent, IMO, best seen with an overnight in the area.
Merida has an extraordinary archeology museum.
Ek' Balam is best seen from Valladolid, charming in and of itself and also near some glorious cenotes (the Cenotes Dzitnup).
Uxmal and Ek' Balam are very different. Uxmal is much, much larger. With only one, that's the one I would choose, but I'm glad I didn't have to choose.

Before you commit to Celestun, make sure you check when the flamingoes are there -- the majority of the flock spend certain months elsewhere.