I wouldn't do a soak. It will just add to the stress they are already under. When they arrive move them into the critter keeper. I would take them home that same day and get them in a more permanent QT setup for at least 30 days. This will allow them to relax and get use to your environment.

They won't eat for a few days typically, but it is always a good idea to have food present for them at all times. Reds only feed at night so just before lights out put 2 - 4 small (no bigger than the length between the frogs eye) in the tank per frog. I fed my baby reds from a bowl. It took them a day or 2 to get use to it, but it allows you to see how many they ate in the morning and removes the odd cricket left alive in the QT tank. Crickets can and will bite your frogs and that is never a good thing. Per usual it is super important to dust their food with vitamin and calcium. I do a Mon, Wed, Fri dusting with Calcium w/D3 and Sat we dust with Multi Vitamins.

In Short - Get all the moving and stress over with as quickly as you can and then get them on a good steady routine.

Oh and I would love to see pics of your new little friends when they arrive! please