St Lucia Vs Cuba?

[Sfin]

I am looking for advice as of which destination to choose? We are going with our 4 year old this May for two weeks and now finding it really tricky to choose between these two. Thanks!!

The Cayos in Cuba are beautiful and child friendly, took DD when she was 3 and she had a fabulous time. Have been to Cuba many times, would avoid the mainland now for the majority of the holiday as the Cayos are so lovely but a couple of nights in Havana is a must. I can't understand anyone going to Cuba and not seeing the place, it's like nothing else. Time stood still and the entertainment is amazing.
St Lucia is also lovely but just not as interesting and obviously a lot more expensive.