I'm pretty sure you are supposed to keep them at home for the 1st week after the spots appear.
I know of a few people who have had chicken pox parties where all the local kids are invited to pick up the virus so they don't get the horrible version as an adult.
Have stayed in. Doesn't help that Mrs Jem is at a Spa Hotel!!! House looks like downtown Beriut! Family lunch tomorrow should be ok they have all had it.