Have you ever tried just olive oil (or grapeseed oil, canola oil, ect) in your hamburger? (If you do hamburger too) Works great and doesn't add the fatty taste to the meat. We grill deer burgers at parties and people are always surprised at how much better our burgers are than beef. And the patties don't shrink on the grill, you just gotta figure out how much oil it takes to hold the burgers together. Hope your friends make themselves useful with the meat processing for your sake.
-Forrest