My memory is it is Christmas Eve, and a mother rabbit comforts her son who is missing his grandpa that died. She goes to the window and waves her hand in the moonlight to cheer him up saying that is what grandpa did for her when she was little.  Then her son shares memories of grampa and says while mom is cooking the next day, he can carry on traditions of what grampa used to do like help the younger kids ride a bike, letting them win games, etc.

Thanks for your help tracking this book down.