I just looked on ebay and you have options.

Best I saw was a set of Mavic Open Pro's, NOS. If they're 415g in 700c, imagine a fair bit less in 650c. Use the hubs and spokes I mentioned earlier. I am hoping it's got rim brakes, discs throws my weight estimates off a bit.

Given the smaller size, that'd put him at probably 1350-1400g for the set. So not scary light but very light and probably just about a bombproof as a set of road wheels can be, he is 11 after all.

Back in my tri-days, I had a Felt B2 (back when it was a boutique brand from Answer) with Hed 3 wheels on it. I don't think he should or is even allowed to rock carbon tri spoke wheels but stuff like that is probably still around somewhere.

Back then, Y2K-ish, skinny tires were all the rage. I know I had 23's on my road bike but I sort of remember my 650 stuff was even narrower, like 20mm. Talk about a pain in the butt to mount. With all the science and attitudes trending toward a slightly wider road tire now, is his new Allez built to handle wider tires? I'm certain my Felt could not have ran 25's. Terry makes 28's, probably the widest 650c on the market. FWIW, 650b is different and you can't fit a B tire on a C rim or vice versa.