Find a currently serving USN flight surgeon (active or reserve). They should be able to get you the CURRENT policies on body dimensions and airframe assignment. Baseops.net might have some answers, but dated info might be out there since policies change sometimes.

Upside to military service is that it will usually be a defining part of your life, and usually a positive. The fact that it runs in the family will only reinforce the positive (and the regret if you don't do it). Knowing that your forbears served makes it easier to get through hard times, and makes it more meaningful (personal experience).

Downside has to do with industry timing. As far as anyone knows, this is the BEST TIME EVER to enter the airline industry. Career progression will be rapid, compensation is trending from high to very high, and QOL is good at the majors. If you go active-duty, you're probably looking at entering airline industry after 2030, when the bulk of the retirements at the US legacies are done.

Basically your timing kind of sucks, but it's a good problem to have, in that you have two good options. My generation grew up when both airlines and military were downsizing. Don't take the industry opportunity for granted, it's a rare opportunity that's hard to appreciate if you haven't seen extended downturns. That kind of money is hard to come by, in any line of work.

It's a bit of a tough choice but I would also consider the Air National Guard or USAF Reserve. You could progress your airline and military careers in parallel, and not miss the airline retirement wave. The Navy (and USMC and USCG) do not train reserve pilots, they only hire qualified military pilots who typically have completed 10+ years of AD.