I'd get up and walk out. It is conceivable that while doing that, whatever drink/food was on the table might end up in their lap or on them.
I also carry pepper spray which might come in handy if I was blocked from retreating. I carry different versions depending on the situation, up to and including a canister of bear spray which is located permanently in the outside mesh pocket of my backpack w/ the nozzle just sticking out so I can reach it while I have it slung on my shoulder. Black backpack, black canister, can't really see it unless you look real hard. When I'm in my car the backpack is on the floor behind the passenger seat where I can reach and grab the canister quickly if needed. If I'm going somewhere "out" where I'm not bringing the backpack then I'll have a larger personal can of pepper spray on me, if I'm just doing my regular routine I'll have a smaller one in my pocket.
Good call.
If you are trying to retreat and the umbrella squad is resisting your bear spray, there could be another umbrella defeating option that's available in any hardware store and in combination with a Zippo could 'light the way' to your escape. I'll just leave this right here...
Wasp spray is flammable - Tractor Talk