The two things he says are... 1) He thinks it will be uncomfortable having something on his face all the time. 2) he says it's weird to suddenly add glasses to his look now.
I told him on both points he will just kind of get use to it.
I didn't tell my parents my vision was getting bad because I was fearful of glasses. Finally, at 12 years old in the 8th grade when I couldn't possibly squint any harder, I told them. (yeah, I was a bonehead)
I was fortunate enough to get contacts. However, I lost one in the 9th grade. And for some unbeknownst reason to me, back in the 80's getting gas permeable lenses took a while to get. So, I had to wear glasses for while.

The horror! Well, it wasn't horrible. Nobody teased me, and I got quite a lot of compliments on how the frames looked.
I can see his why he is not thrilled, I was right there with him. As for his concerns:
1. Like you said, he will get used to it. After getting used to the depth perception, he will likely feel the glasses pressure the most on his nose and behind the ears. A few days and it will be nothing. But prepare of a few days of complaints.
2. I get that one. A new look when you don't want a new look is not easy. My only suggestion is to shop around. Go to places that have a wide selection. Have him try on lots of styles so he can see which one he likes best. If you go to just your optometrists office it may be very limited. My daughter loves her glasses she found at Lens Crafters, we went there after zero luck at optometrist's office.
I hope he finds a pair he falls in love with, and am sorry he is not allowed contacts.