- Send them affordable Bitcoin on their birthday.
Give them bitcoin as a gift, but not on birthdays and valentines days and Christmas and stuff. A gift(especially for these special days I've mentioned) are mostly something to make them happy; not an opportunity for you to shove down your interests to them regardless if you have good intentions.
I agree with you totally on this. Its a special day for them, and they will appreciate something special to them, not you. Since they have little or no knowledge about Bitcoin before now, I doubt if they will really appreciate or value your gift.
Maybe some other day, you could educate them about Bitcoin, but certainly not on their special day.