J.P.
Hi Kara,
I think grandparents love homemade gifts from the grandchildren the best. Maybe personalize a craft with a photo of your kids such as an ornament. They have garden stone kits that your kids can make with your help. You can buy these at Michael's, JoAnn's and Hobby Lobby. Your kids can stick their hand in the cement and make their handprint and they can stick in jewels.
Or have them decorate a large tile and decorate it with paint that can tolerate heat. This can be used to put hot plates on at the dinner table. You could also put their photo on a t-shirt, mug, etc... but this wouldn't be ready by tomorrow.
Slim chance here... but does your husband have a cousin named Dana and is your mil's name Lizzie?
Take care,
J.