I've had similar problems while takeing kids on campouts.
Bears are naturally curious and always hungry. They are feeders of opportunity and smart enough to pick up on any easy meal. They mostly feed on grass, but will immediately jump on any opportunity to feed on anything else.
As far as slugs in your shotgun go, "if all hell breaks loose". You are going to be shooting under 30 meters. At that range, a slug will tear right through a bear and keep on traveling with a lot of retained energy. I would suggest that if you really have to shoot the bear, which I personally have no problems with, use SSG or Double O Buck shot. At 30 meters or less, there wil be a pattern of about 40 cm and very few if any of the pellets will emerge. You may miss with a few, but they won't create anywhere near the problem of a slug. If it hits the fan, you won't be looking for an adequate backstop or direction to shoot.
I've shot bears as close as 3 meters with 00Buck, it flattens them on the spot, at 25 meters it does the same thing.
The big thing is remain cool and use your head, nothing intended here, if you deal with kids, that's a given. But bears can and will change in an instant from trusting to scared and aggressive.
Personally I would suggest you deal with the problem under conditions you create. Not knowing where you're situated, it shouldn't be a big deal to set up a very frightening situation for the animal, depending on habits or hunger, it may have to turn lethal. Either way try to control it as much as possible.
If and when the situation is allowed to denegrate to the point of attack or damage, the situation is already out of control and anything can happen.
A friend and I had a hungry/curious bear come into a tent in the middle of the night, what an explosive situation that turned into, includeing a knocked over stove and blood (not ours) all over everything. The bear had been hanging around for a couple of days and even followed us over the hill to a new campsight. I learned very quickly, right then and there, get control of the situation before it gets out of hand.
bearhunter