We went for Xmas a few years back -pre dd - and stayed 3 nights in Havana and 10 in Varadero. Havana was fascinating. Varadero was fine - but you could have been anywhere with a nice beach. The food was not that great, which made me feel mean as it probably better than the locals get. We drunk a LOT of rum squishies.
I've been with my DC and enjoyed it. We stayed in Playa Pesqero for 10 nights and then flew to Havana and spent 3 nights there. Havana was really fab. I can't think of any reasons not to go. Was you thinking of having a resort based beach type of holiday or more of a touring holiday? Mexico would also be really good, I have been to a few places with my DC on the Pacific coast and would recommend Cabo San Lucas and Peurto Vallatra.
considering for xmas 2013, tickets already up 100 pounds a head since i last looked, not an easy decision to swallow, anyone have any convincing arguments for or against with kids 16 13 and 10 (we always take our big holiday at christmas, previously have been skiing x5, thailand x2, egypt, sri lanka and morocco. considered mexico but cant get my head around which part in order not to be in a heaving resort)