There are several ways of looking at this . If the house they want is a saleable product , but they want the source files then charge a suitable price , time and materials , taking into account how much you stand to make from the product and specify in the sale to them that you retain rights to the product.   If you just made it for your own use then recover some of your costs by charging for time .

the other way is to contract with the that you will DONATE the files , with an agreed value , so you can get a tax deduction , AND your name and contact information will be displayed on the exhibit, so you get advertising benefit from it. 

They will be doing all the work , so you just need to decide how much those files are worth to you . It could be worth finding out if other museums might be interested as well. Dont give the museum rights to distribute anything made from your files .