As we all know, most Cubans don't have much, but they try to do as much as they can for the kids. If you have the baggage allowance, a good idea is children's clothing and shoes, as well as those for adults. The kids grow out of their stuff so quickly that the parents can hardly afford to keep up.Bring some name brand stuff that they only hear about. That will get them excited. Many of these girls have kids so something for them like candy will be appreciated.
I usually take as much as possible, get good condition used clothing from friends and relatives, and when I meet families, I try to make a liitle package that will suit them. Toothpaste, toothbrushes, headache tablets, vitamins, colouring books, pens and pencils. Almost everyone seems to like chocolate and chewing gum.
For the girls/women, you can find low cost clothing items at H+M, lingerie stores often have sales for underwear.
Batteries, battery chargers, baseball caps, tennis balls .. the list goes on.
I generally leave a tip for the chamber maid, they get more than enough gifts, stuff left behind etc. I always try to find people who aren't hanging around the tourists to give stuff to.