Your heart is in the right place but when you say things like, "... how do I go about identifying the people most in need without going to a potentially dangerous part of town?" you're demonstrating shocking naivete as yo how to handle gifting in a poor developing country, especially one that's as complicated politically as Cuba.

Impossible to guess how Aduana (Cuban Customs) will react when you give no clue what you're bring. There are no such things as NGOs. Never, ever gift to anyone who you don't know, especially children. Casa owners are indeed top of the food chain and absolutely do not require gifting.

*"I also feel like it would be weird or insulting to just walk up to some Cubans chilling on the sidewalk offering donations lol." You're right, that about as irresponsible and disrespectful an act as you could possibly do.

Forget about reputable websites. It's Cuba. The internet barely exists.