Oatmeal baths. As long and as frequently as he wants.
And, slather him in vitamin E oil w/ a few drops of lavender oil in it when he gets out. Maybe put a few drops of the lavender in the oatmeal bath water, too.
The vitamin E helps w/ healing w/out scarring and itch, the lavender oil is antibacterial (and calming), should he scratch at all.
That's what I did, for two weeks, last Christmas. :)
I wouldn't worry about going to the doctor if you know it's the pox. Once you find one, you could always ask them to do a varicella immunity titer to get it into his record.