I take my piggies to the vet in a large cat carrier. I put a large pee-pad (or two smaller ones) in it to cover the base, but have also used a folded bath mat in the past. As long as it gives them some grip and absorbs pee. If you have nervous piggies you can use a pee pad straight from their cage so it has a strong smell of home. Then put in a handful of hay so the piggies have something to nibble on and to hide in.
I put the carrier at the footwell of the passenger seat in the car and cover it with a large towel to both make them feel safe and to reduce airflow from the heating or A/C. And then push up the passenger seat to the carrier so it doesn't move if I have to break suddenly.
They will be fine for 2 hours without water, but if they are used to it you can offer them some cucumber to keep them hydrated.