Can Kebabs be frozen?
Meat, as long as it's fresh, can be frozen without fanfare.  Vegetables are another story.  Usually they need to be blanched and cooled before freezing (to stop enzymes from causing them to mature past their prime).  However, peppers and onions are fine to freeze "as is". I am concerned, though, that you won't like the vegetable quality once they are defrosted.  You were on the right track: all vegetables, regardless of the type, sustain at least some cellular damage due to the freezing process.  So cooks usually only use the items in dishes that don't require a "showy" performance (like a small dice for salads, or in cooked products like soup).  The reason for this hit in appearance and crunch-ability is this: Veggies are mostly water (70-95%, while beef is only 55-65% water).  As veggies begin to freeze, the water expands, causing tiny shards of ice to break through the delicate cell walls.  The partial or total collapse = mush.

One additional concern is freezing the kabobs with the sticks still in.  Whenever freezing food, you want to keep all moisture IN and air OUT.  (Air changes flavors and distorts color).  This means that whenever possible, you want to pack items in air tight containers.  Obviously all the "empty space" that pre-threaded kabobs require would introduce all sorts of air into the storage container.

If I were you, I would disassemble the extras: freeze the meat to use however you like, and the veggies for less looks-dependent dishes.  Or -- just go ahead and grill up every last kabob, then send your guests home with leftovers.  (They'll definitely come back again this way.)