Should we euthanize our elderly male dog since he's getting grumpy and growls at our younger dogs?

We've had Duke since 2003 and he's now 11 in people years. He's always been good natured and just a sloppy old dog... St.Bernard/Chow Mix. For the past couple of months since we moved from our old home, he's been snappy and growls at the other dogs when they walk by him or he thinks they're gonna eat his food. He is NOT aggressive with people at all, but we think he's getting senile and may make a mistake with our son, and not mean to. Should we have him euthanized, or just let him live out his days? We're torn because we love him but we love our other dogs and our little boy.