Even though in a few years this age difference won't matter, now it does.
I think at this stage it might be best to just keep it to a level of good friendship. Enjoy going out together in a group or even if it's as a couple, just keep it platonic.
As PDM said, there's the legalities of it as well to consider and we all know how people love to talk, and the wrong word said to the wrong person could cause a lot of heartache for everyone.
Also your friends and his could start teasing, spreading rumours etc. because of your ages, so be prepared for that.
Much depends on the maturity level of each person and of course the parents. As your mothers are close friends, they might be more than happy to see you both together.
He sounds a nice young gentleman to have paid you a compliment like that and often these days, those positive comments are far and few between so I can understand why it meant something to you.
