Boy that is a tough deal to swing, especially without spending a few extra points. I know the idea of a family hunt sounds like a lot of fun, but I'd strongly consider letting your boy maximize his 9 points and let your brother hunt something near by this year, and consider using your points on a 4th tag in a year or two in a unit you can maximize your points.
Unit 68, your boy will draw but be wasting a point or two. You will have a chance but not guaranteed since there were 12 applicants with 15 points last year and 2 of 3 applicants with 16 points didn't draw. The tag quota was four last year. So that would mean 2 of the guys that didn't draw last year will draw this year with 17, and that leaves 2 tags for you and the 15 other guys sitting at 16 points. Risky at best, but maybe a decent option if willing to wait a year or two. Not much option for your brother other than an OTC elk tag for 3rd season in 68 or a landowner 3rd rifle deer tag in 79 depending on his financial situation. If you guys did wait a couple years to guarantee your tag also, he may be able to draw that 79 3rd season with 2 or 3 points.
52/411/521, you and your boy will both be able to draw your 3rd and 4th season tags, but you will be wasting a point or two and he will be wasting about 4 points. Your brother would have about a 50% shot at 41/42/421 3rd season tag or could OTC elk in 52 3rd season.
Good luck with what you decide.