Weddingbee boards

My FI will be wearing this vest with a white button up, matching grey pants, and possibly one of these two colored ties.  Of course it will match better once I take the vest out shopping. :)  But my question is what should the groomsmen wear?  Unfortunately this vest runs somewhat small and we aren't sure all the groomsmen will be able to fit in it.  My FI would normally wear a medium and the vest we bought him is XL.  Initially we thought the groomsmen could just go buy a grey vest and matching pants (much like the mismatched bridesmaid dress concept) but I'm not sure if this will work.  Will it?  Are there are enough different grey vests that we could find 3 more different ones?  Or should my FI return the vest and get one that runs true to size and have all matching men?  I can tell you right now he won't like that idea. :)

They definitely don't have to match- it's HIS special day too (my humble opinion). Hmmm, if you are having a more casual wedding, you could just have the groomsmen in shirts + ties. It's an idea. But I'm sure lots of Bees will have good ideas for you :o)