I think general noises of sympathy and empathy are the only thing required.
Whichever person is in charge of organizing the gathering can certainly contact the company again, maybe try the "human interest" angle of MIL's attachment to the place if they think that will work. Otherwise the organizer's obligation is just to find a location that's logistically suitable (price, location, etc.). Maybe the organizer could ask MIL what other things she liked about the place--I think I remember from another thread she was keen on their big garden? So perhaps the organizer could focus on places known for their garden spaces. At some point, though, lukewarm or not, the organizer will have to settle on a place so all the other people in the family can make their plans.
Also I think if too many people get involved in trying to "fix" the situation, without coordinating with each other, it could lead to a mess and hurt feelings.