Question: Is it alright to make light offerings at my Buddhist shrine for living and departed family members together?
Answer: There is no teaching against this. Anyway, on behalf of the living and departed, all lights are offered to the Buddha(s) to create meritorious virtues. It is not possible that the perfectly compassionate Buddha(s) accept one kind and reject another kind, or offer blessings to one kind and not the other kind.
Out of courtesy, as they are meant for consumption, food, fruits and drinks should be offered separately, in different receptacles, as placed before Buddha(s)’ images and tablets of the deceased. Even though the Buddha(s) do not literally consume them, this is done to express reverence, and to not create confusion for the deceased, if their consciousnesses are still around. Otherwise, they might accidentally ‘steal’ the Buddha(s)’ offerings when they are consumed by inhalation.
When you make offerings that can be consumed, be specific in your prayers. If there is only one portion, you can say they are ON the behalf of so-and-so, FOR the Buddhas. If you think there might be deceased relatives around, it is better to make a separate offering on another plate, perhaps next to the Buddha(s), without confusing it with the plate for the Buddha(s), right in front of the Buddha(s).