You'll have no issues from banking point of view. If he doesnt already have a bank account, you might consider speaking to the bank about their treatment of vulnerable customers to see if that might be an appropriate approach in the case of your son. Having it flagged should mean they will take the appropriate time to explain things with him, and depending on the bank the auto flagging of suspect transactions.
However, you need to have a look at the transfer from a gift tax point of view. No issue if the money was obviously always his (easier to evidence if the money was segregated into a separate savings account for example).