First of all – how wonderful that your 22-year-old is still taking your advice! The truth is, he’s a full grown man and most men do what they want without their mother’s consent.
My rule of thumb has been to pick battles wisely.
The motorcycle should be strongly discouraged because in my view they are death cycles (sorry to all readers who are motorcycle fans.) I’ve seen far too many deaths or serious injuries from them. That leaves the tattoos and since many teens and young adults love them, give in.