Personally, I would never send money in an envelope. One can feel it's a card, especially those with badges attached, then there's a big chance it's a birthday card for a child, and chances are Grandma / Gramps are sending some cash, too.
I would send a message to those family members, if they are thinking of sending any money to write it out as a cheque to you, in your name, if they are not familiar with transferring money online, then you can bank and give the cash to your son.
That's the only way to be safe here.
@soccerbuy
