I think it’s normal to worry about how something like this might be hard on him in some settings, I think the more you can genuinely work on this in yourself the better off he will be otherwise he will pick up on some of your fears/potential pity/worry. My husband is 5’6 and my dad is 6’5 (along with the rest of the men in my family) so just saying I was very used to being around tall men and it still didn’t matter. And it truly doesn’t seem to bother my husband. He’s like cool I’m short. Some people are tall. His family never made a deal about it and it just was the way it was.
If he has moments in high school or middle school where he struggles with it (especially having tall brothers) be empathic, listen, but not overly like “don’t worry!!! You’ll still be able to date!!” Because I think that will come across as yes I agree this is kind of a problem but you’re still goi to be ok. Instead, listen, reflect back, say woof sweetie I know it can be so hard when you feel different. What is it your most worried about? And keep asking questions like that, help him through his worries. Also know he may never have these worries! I’m not kidding that my husband does not care.
It matters so much less once in adulthood. So focus on working on yourself and your perceptions of short men, which it sounds like you’re doing. My husband is kind and a great father and I wouldn’t take a tall guy over him any day