this is a very good idea, just make sure that you know everything yourself so you can answer their questions easily.


there are a lot of ways, most popular one is to give away a paper wallet you made yourself. especially with a nice print and a short help on the back of it about how to spend the coins by sweeping the private key you give them.


the smallest amount (if i am not mistaken) is the dust amount which is around 5600 satoshi.
but you should give something away that has a real value like at least $1 anything lower than that is not even worth giving since they can not really do anything with it.