The premise itself is the tricky part here - it's not really about whether it's weird, but about how you frame it. Your friends will take their cues from your confidence. If you act apologetic or tentative about the rule, they'll feel awkward. If you just... have it as part of your home like it's normal (because for lots of households, it is), they'll adapt instantly.
That said, there's a difference between "we prefer shoes off" and actually enforcing it. The earlier answers are right that casual mention works, but you might avoid sounding like you're policing anyone. "We keep the place shoes-off, there's a rack by the door" is just information. Some guests will respect it completely, a few might ask to keep theirs on if they've got bad feet or whatever, and that's fine too. You don't need to be rigid about it - just set the default and people will follow.
The real trick is actually having somewhere obvious and comfortable for shoes. If there's a decent shoe rack, hooks, or even just a clear spot, people see that and immediately understand this is intentional design, not you being weird. No rack? Then yeah, it suddenly feels like an imposition. So before you worry about social awkwardness, make sure the logistics actually work in your space.