I live alone, and frequently cook "normal" sized meals and pop in the freezer. Meat loaf is one of my favorites. I, too, bake in muffin tins -- quicker and portion control! lol After they are cooled a little, I just put them all in a gallon-sized ziplock bag and pop in the freezer. There is so little moisture in them, they barely even stick together. Then I can take out 1 or 2, warm, and dinner is rolling!
I don't use gravy on mine -- preferring ketchup instead

; however, there are a lot of frozen entrees which have gravy on them (including biscuits and gravy for breakfast), so I can see no reason why this wouldn't work for your family. If it's a cream gravy, there probably will be some separation due to the milk in it, but just stir after it's warmed up!
Good luck, and God Bless You!