Death in family while away at basic training...?

Well, my husband is away at ft. benning, GA for basic traing right now...his grandfather just passed away. Now, his mom told me not to tell him and for him to just finish what he has to do but I just know that he would be even more hurt finding out on family day a month later that he lost his grandfather and everyine had been writing to him as if everythings fine when everyone knows except him... What do I do??? I know he's looking foward to family day and it would just ruin the whole happy expectations if he found out then. Someone please help. I need advice for the sake of my husband.