The MK2 214270 is much nicer with the lumed numerals compared to the MK1 white gold numerals. This would make sense from the view that your son, being the modern version of you, has the modern version of what you have. It can be a bit underwhelming though and my FIL calls mine a posh Seiko.
The 42mm Explorer II is thinner than you'd think and wears very flat, not a saucepan but can depend on how flat your wrist is. The black is much less popular than the white and given you don't know how niche your son's tastes will be it could be more of a gamble than some other safe choices. When I had an 42mm Exp 2 I went white as on the black I couldn't get my head around the floating hands. A matte dial with the black metallic back-end of the hands didn't make sense to me as that stood out too much. Less popular now could be the best buy with 20 years of hindsight?
A guess an obvious one that again might be a bit underwhelming would be an 34, 36 or 39 OP in white. The next obvious one would be a no date Sub but who knows what age he'll be by the time you get that.
Either way congratulations and I'm sure when the time comes he'll either love it or join TZ and list it for a profit