I wasn't too sure about how to word the title of this post.
So you can go 2 ways with this. You can either hire suits or you can buy them. If you decide to go for traditional tails, I recommend hiring, unless you can think other events you'd be able to wear the suit for.
Another thing you will need to consider is who will be wearing wedding suits. Now, as I had a small wedding, only my groom had a formal suit and it looked right. I've been to large wedding in the past an there have been quite a few groomsmen. These include; groom, best man, father of bride and groom, ushers, and any male siblings.
If your hiring a suit, I'd reccomend your guys get measured and fitted a few weeks before (not too early though). If they already have shoes (not all the shops hire out shoes - mine didn't) make sure the men take them to the shop as they could change the way the trousers hang.
Once you collect the suits, make sure all the men are with you so they can try them on and if there are any problems the shop can deal with them.
Hope this helps!