Of course it is doable. It is up to your son to prioritize his grades, but that is true of all students. The average GPA among Greeks is consistently higher than the average GPA of all male students. (That is true of a lot of organizations, of course, since students who are flunking out typically don't join many organizations). If he finds the right chapters that emphasize grades, then his goal of a high GPA will actually be an asset.
Here is a link to the Spring 2017 grade report, which is the most recent I could find online. I would say, focus on the chapters that averaged a 3.00 or above, and just ask questions during rush about how much the chapters encourage academic achievement. They almost all claim to encourage it, but ask them what they actually do.
https://www.union.msstate.edu/sites...les/Fraternity Grade Report - Spring 2017.pdf
I graduated with a 3.86 in Chem E, and there were a couple of AE's in my chapter who had a similar or better GPA. Plus, the chapter had upper classmen who gave me valuable survival tips, and helped me seek membership into leadership and scholarship honors chapters around campus to become more well-rounded and pad my resume. I never would have even heard of some of those possibilities if not for my brothers.
And when I decided to switch gears as a Senior, my fraternity brothers helped me figure out how to get into Law School.