You will need to get an international romaming add-on.
For your phone, the cost of the add-on is 15$ for 75 outgoing texts from Cuba, incoming texts are free.
For your husband's phone, the cost of the add-on will change based on whatever length he will be there. All the add-ons are for unlimited texts while in the US, for either 3 days (10$), 10 days (15$), or 30 days (20$).
If you are going to just do texting, you don't need to worry about other add-ons.