Tell them if the dog approaches them, to not scream or run. There is no way they can outrun the dog and this could provoke an attack - the dog night see them as prey. They should stand like a tree, and gradually back up to safety. Should the worst happen and the dog attacks, to roll up in a ball and protect their face and neck. To play dead, until help comes.
Dogs running in packs are more dangerous than a single dog.
If one attacks, the others join in. A pack mentality develops even in dogs that are otherwise not aggressive. The most dangerous situation can be a dog that is tied to a stake. Should your child enter it's small territory, the chances of being bitten are excellent. Staking a dog can make the best of them aggressive.