I don't even know if ushers are really a "thing" anymore because they haven't been at wedding I've been to recently, but my two brothers are going to be ushers for our wedding. Most of the weddings we've been to the seats are kind of a free for all anyway, but our guests will be seated at their reception tables for the ceremony minus the immediate family in the reserved rows of seating so I think in our case having the two boys help guests find their seats will be helpful.
If the groomsmen are wearing suits, would the ushers wear suits too, or could they do dress slacks, shirt, and tie instead? One of them has already asked "do I have to dress up? Can I wear my work boots?" and the other wants to know if he can wear his Dr. Who tie (not quite going with my theme here, buddy.)