Like most that have replied, all gave great advice, tips etc. I have also rode for over 35 years, on everything.
Amature road raced several years on CBR1000 RR. Only going to comment on couple of things, no replacement for experience. Nothing can’t turn a great planned trip with your son into nightmare quicker than an accident and serious injury. That said, buy good safety gear, helmets, gloves, jackets and even good riding pants. I would highly recommend after buying your choice of bikes take an entire summer and just learn to ride and control the bike. Take short day trips, go out on days that’s it raining so you know what to expect and understand that your riding speed and how you ride will need to change, slower in corners, not snapping throttle open coming out of corners, which will spin tire when wet., etc.
If a situation arises that you need quick action to avoid, your reaction needs to be instinct and second nature. You will not have the time to “ think it through” it will be over long before that. Most of the accidents on motorcycles are not the fault of the motorcycle rider , but the other driver that did’nt see you. I think it is awesome you are going to do this, just make sure both you and your son have the experience to go and comeback as you left. Good luck and Godspeed.