I'm going to disagree a little bit...
My FI's gifts for his groomsmen are their clothes (shirts, pants and flip flops) for the wedding. Last fall I emailed all of them and asked them their sizes so I could order their stuff. I thought it was a great idea (so there was no confusion with the wedding attire and it was all done correctly). BUT, I found out afterwards that my FI didn't like the idea and would have rather gotten them something "cool" (but went along with my idea b/c I had already informed his GM of our plan). When he told me that I felt really bad b/c he doesn't care much about wedding planning and apparently he was upset. Long story short (well not really), I think you should take FI's ideas into consideration. If he would rather take care of the GM's and all of their wedding stuff, let him (but just be sure to follow up with him to make sure everything is getting done).