You can be reassuring. You can't reinforce fear, only the behaviours associated with it. So as long as they're not vocalising, weeing or being destructive it's fine to reassure them, as you won't be reinforcing behaviours you don't want them to repeat.
Let them decide where they feel safe, even if it's somewhere they don't usually go.
My old girl used to squeeze herself between the back of the sofa and dh and I, but wasn't usually allowed on the sofa. She needed it to feel safe, so under those circumstances it was ok.
Close the curtains and put the TV or radio up loud in as many rooms as possible, not just the one you're sitting in with them.
Re Saturday, yes, if it were me, I would stay at home with the dogs and dh would take the dcs. In fact it's my puppy's first bonfire night and I will be staying at home while dh takes the dcs, as the display is at the school across the road from our house and guaranteed to be loud.
For next year you can try Dorwest Herbs Scullcap and Valerian and get hold of a sound effect CD or download an MP3 to gradually desensitise them to the sounds well before bonfire night. You could also try a Thundershirt. They sell them at Pets at Home and have a no quibble returns policy if the don't work for your dog.