That sort of damage is pretty much beyond repair - sorry. Although I can't see clearly enough from the angle of the photo, it may be possible to remove the damaged portions above the graft and still retain the weeping laceleaf portion but the growth habit has been seriously compromised and I doubt you will be very happy with the looks of the little trees going forward.

I'd suggest replacing. There is always a risk of damage from snowloads on these types of JM's because of the way their branches form that layered framework for the snow to rest on. Careful pruning can help but your best protection is to stake above the crown of the tree and cover with a tented (steeply pitched) covering (like a tarp) so that the snow slides off to the side.

Some people bolt the split back together. Google "split Japanese maple bolt" and you'll see some tips. I agree, though-- that's pretty serious damage.