When I send text messages to my children, I end them "Love, Mom." If they said "Love Mom" that would be an instruction to them to love me. Since what I mean is love FROM mom, the comma is needed. However, since "thanks" is not a verb, there is less chance for confusion, but I would still include the comma. ALso I would capitalize Mom and Dad and Aunt Iris, which refer to specific individuals in this case, and thus function as proper nouns.