Those things would make playing a guitar difficult, and that's one of the kinds of dexterity I normally associate with arcane spell failure.
And yes, I know there's an open can of worms here.
Caveat: I've assumed that we're talking 3.X. If you're designing for a clone and I missed the tip-off somewhere, sorry for the poor language skills. Haven't had my second cup of coffee yet.
That warning in place: there's no such thing as a "shield slot". A character can wield as many magic shields as their hands allow. But they only get to count the biggest
Shield bonus to their AC.
It seems to me that the AC bonus from these gauntlets is the kind of thing that wouldn't stack with a buckler. Going form that to typing the bonus
Shield makes them slightly more attractive for two-weapon fighting, but I tend to think they were already going that way.