I second the AC above. (Replying to you so you get the notification). Donate them locally. A few computers or clothes wont make much difference and will probably not reach the intended target. Trying to get Customs to release computers is not fun, even if you have all the paperwork in order. Been there, wouldn't want to do that again.
Now, if you plan on going to Cuba and have stuff you want to give away, by all means, carry extra clothes and a laptop. Check what you can bring in without paying extra and pay attention if they write down the details of the laptop (it may mean that they are going to fine you if you don't take it with you. I've never seen that, but I've heard stories). If you fly in to a small airport, most likely no one will bat an eye. Don't stay in a hotel, stay at a B&B (I hate the name tourists give them, "casas particulares"). Hopefully it will be obvious who will benefit the most from your gift. Just keep in mind that those who work with tourists (e.g., your hosts, bartenders, etc) are statistically better off than those who don't.