Sorry about the accident and your hubby's situation. Hope you guys are holding up ok. I'm not familiar with what happens in a lawsuit, but I imagine the person who actually hit the students would be the person to be sued primarily? We have a few lawyers in here, hopefully they can shed more light.
I would not speak about it, give statements or admit to anything, etc without consulting a lawyer. As a witness, you must show up to court. Otherwise, they will issue a warrant for your arrest which can't be good especially as you're sponsoring your husband.
Keep record of the visits because it can be used as proof of a continuing relationship with your spouse. If they serve a purpose for the accident/lawsuit, then no harm done.