No, multi-hit weapons aren't able to crit (felt they would be too OP otherwise, especially if combined with a potion of luck)
Is each charge of a potion of luck not consumed by each roll of a multi-hit weapon?
Multi-hit weapons don't even seem to deal that much total damage compared to many other weapons - as it is, there's no reason I can see they shouldn't have the +5% expected damage increase that every other weapon gets, as long as each crit only doubles the damage of the roll that landed 20. If a 40 damage sword gets a 1/20 crit, no reason the 10x4 damage dagger shouldn't have a 1/20 to crit with each hit.
Unless, of course, effects like the lucky potion don't work the way they say they do, which would be the real issue if that is the case.
Edit: not like any of this is a big deal lol just found it confusing.