Our Honda has a radiator leak- what can we do to temporarily remedy this?

Well stop-leak additive will definately slow the leak (won't fix it) but you should know that it's a much higher thickness/viscosity than normal radiator solution and if it's leaking on the exhaust manifold it's going to produce a much darker cloud of smoke and on top of that it will smell awful. So if you're planning on using it just keep that in mind.