Do your homework on what pressure the small tank is supposed to handle and what the pressure in the big one actually is...

If the difference between those two numbers is too great you need some kind of pressure reduction valve - or a good guestimate of how many seconds you can leave the connection open before the pressure in the small one gets to dangerous levels.

I don't know about the specific tanks you're thinking of refilling. Coleman propane tanks looks quite robust to me, if that's what you have in mind. Those flimsy light weight canisters (butane / propane mixture) is a totally different ball park - their pressure is MUCH lower than tanks for pure propane.