I'm pretty sure I have some 10-32 helicoils in my box of stuff, which is what I'd use. 10-28 is an uncommon thread pitch, so I'd confirm what you have first. If you do drill for #12 screws, match the pitch to what the #10's are (10-32 fine or 10-24 coarse).
The #12 screw heads would look weird, being bigger.
