Try make it hard for him to grab you in the first place. Falcon grab has awful range, so they'll usually dash beforehand for forwards momentum to ensure it won't whiff (dash/JC grab). Don't have much experience in the Falcon MU, but spacing needles and sticking to moving around different plat heights would make it probably give him a harder time getting grabs. Throwing out hitboxes like spacing Bairs and AC Fairs in place help to. That way, if you do discourage him from grabs, he'll only approach with hitboxes or space around you. Shield and punish the non-grab approaches, and needle him to force the approaches if he's just spacing.
If he does get a grab, there's the usual DI away and DI in mixups, but there's not much you can do to avoid the Uair/Fairs afaik.