There is always someone in a family who tries to, or thinks they have the upper hand, what they say goes. Well they don't and it doesn't. Simply say that for the safety of everyone you don't think this is a good idea and will be happy to join in festivities when all is safe and clear. Have a Zoom call, let them send photos, phone and chat while they wait for their lunch. Send cracker for the 92 year old. There are lots of ways to show you care. The rest of the world will (mostly) be doing the same. You are not alone, we are all having to forgo some fun, just for now, for the sake of keeping everyone safe and getting through this as soon as possible. Good for you for even thinking this is a bad idea, be brave and stand up for yourself, politely and kindly