Sorry can't comment on the accomodation.
For that time of year, I think the weather is more or less guaranteed.
I ususally go either at the start or end of the season (May or Sept/Oct)
Never been to Alcudia so I can't compare, but I have found Es Cana to be just the right resort for myself.
It is very much family orientated. A few clubs, but nothing like to the extent of San Antonio.
Plenty of bars with their own entertainment at night.
Plenty of eating places for most tastes.
There is enough going on to keep people occupied without the excesses of other resorts on the Island.
It has a very good and safe beach.
Santa Eulalia is just a short hop away either by Bus, Ferry or if feeling energetic a walk along the coast.
Santa Eulalia has more to offer than Es Cana in terms of shopping and up market eating places.
Each Wednesday there is the Hippy Market at Es Cana and stopping in resort give you the advantage of getting there early to avoid the rush of incoming trippers from other parts of the Island. The resort does get very busy on Wednesdays.
Hope that is enough for you to be getting on with.
Have a good holiday.