From everybody I've spoken with, and what I've read on the Internet, there is no problem for a US citizen going into Cuba - from Cuba. A lot of trouble from the US - you are not allowed to spend any money there. From friends here in the US who went there by plane, via Canada, you will be welcomed, your money will be welcomed, and anything else you might wish to giv e or trade will be welcomed. Just don't let the US govt. know you're giving aid and comfort to the "enemy".
I understand that women's cosmetics, particularly lipstick, is a welcome gift or trade item. Actually, most consumer goods are in short supply. Lots of Canadians go there for vacation - it's cheap.