I think you'll like it. Make sure you get more dives in similar environmental conditions first, especially your son. Cold water changes things in a hurry, from breathing, to mobility in a thicker suit, etc. So some colder quarry dives until you're really comfortable and not "ready to quit".
Warm to cold is a big transition every time unless you dive cold a lot. Get used to it and learn to enjoy that it's different than warm water sight seeing, you'll experience much more.
Wholeheartedly agree!
My advice to you is to spend a few sheckels on an Inst. or D.M. who is conversant with these diving conditions. He/she can review your entire kit ( suggestion: go to the hip & buy some personal thermal protection for you & your son - a proper fitting 7 mm worn on surface is a bit confining/uncomfortable, but u/w should be warm & comfortable ) & offer recommendations, they then can take you into open, colder water & do proper buoyancy checks, then review some basic skills with you for the purpose of building your confidence/comfort levels when using cold water equipment. I'd further advise to take this process one step farther & spend a day on the river with a dive professional as your mentor/guide. You will learn a lot, your confidence/comfort levels will exponentially increase, and you'll have... FUN!
I've done exactly this for many folks over the years & the response has always been very positive.
As an added bonus, you'll get to see some amazing shipwrecks!
Regards,
DSD