How about pouring a libation outside? It's very traditional in your religion, it wouldn't be something left out to make your mom uncomfortable, and it doesn't have to be expensive. I used to offer sparkling grape juice as a replacement for wine when I lived at home and was under 21. Honey, juice, oil (like olive or almond), milk, or tea would be very easy to get and only cost a few dollars.
Libations are FANTASTIC. In a pinch, you can make it look like you're just watering plants. (Yesterday I offered a bottle of beer to a tree - I can only imagine what I looked like to passersby.)