I would go so some local stores and as for cardboard boxes of different sizes. Then stack, drape with batting and arrange your village on them. Perhaps you don't need to use ALL of your collection or use different ones in different rooms. You can make your mountain village as large or small as you want to.
P.S. My mother passed in January of 2003 and Daddy got killed 5 months to the day later. The first few holidays are the worst but the pain will lessen eventually. Instead of remembering it as the time that you lost your mother try making it a celebration of the life she lived. Include something of hers in your decorations and just say to yourself or even out loud, "This is for you, Mom." Make new memories with your grandson for him to cherish as much as you cherish the memories of your mother.