My dad wants to get a tux for the wedding and suggested FFIL and both grandfathers wear tuxes too...I don't want to ask them to get a tux/think they are pretty un-needed for our not very formal wedding. Groom + male wedding party people will be in tuxes though because that's what FI wants.
So, the main question, will it look weird if my dad is the only one in a tux besides groom and groomsmen? I don't really care all that much, I just things its a bit odd/don't know how much to bother trying to convince him that a suit is just fine (he wears a suit to work most days, so he might just want to get more dressed up)