I think they should just take his name off and leave his late wife's.
Why? It was not her money that paid for it.
Sure it was; although, technically, it was their money, as a couple. And so, to remove either name now, hers or his, removes the memory of half the couple's contribution and work for the community. Not cool.
AlwaysQuizzical's idea is a good one. If he's that concerned, make a new donation somewhere else with the new wife's name. That would be a classy thing to do.