It’s always best to alert your host (or hostess) ahead of time of any special needs you may have. They may be able to solve the problem before it becomes one.
One possible solution is to purchase ahead of time slipper socks with a leather bottom. Your husband can remove his shoe and slip the sock over the brace. This doesn’t give him the complete support of a shoe but may prevent an embarrassing fall.
If he will allow it, he should take your arm for support while walking without the brace. And though many older adults refuse to use a cane, it can be very useful when traveling. It gives a visual but silent message to your host and other guests of special circumstances.