Hi, having been through all this twice, I suggest a relaxed evening, cuddle and wind-down time. The morning will come all too soon.I had bought both of them a small toy(teddy key ring) as a good luck charm, and said that I would be wishing them well through the charm.
I think an early night, and a good sleep will do more good than any reminder cards or last minute cramming. My DD wanted to take strawberries in a pot for snack time, and didn't want any mention of the test before bed.
In the morning, I let them decide what, or if, for breakfast, and on the way in the car we just told them to stay calm, to try to imagine themselves alone, and tell them we knew they would do their best, which was all we hoped for.
For both of my DC I stayed in the car outside, armed with papers, books and coffee in a flask. They both said it made them feel comforted to know we were only a few yards away.
Everyone will have their own ways and ideas, but ours worked for us.
Both my DC were calm, and didn't panic or get upset. They said the charm worked for them, when I asked them tonight, also the fact that we were calm and confident.
good luck to you and especially your little ones.