itchy bumps on my children

Two of my children were outside playing in the back yard.  A day or two later, itchy bumps begin to appear on sporadically around their bodies. A few were on my daughters face. Barely visible. I thought maybe mosquito bites. When the bumps go away they leave a white fleshy round circle as a trace. Now all of a sudden 30 bumps just appeared on my son's left leg and is spreading to the foot. They have little scabs at the tip of the bump. My children scratch them.  I've tried benedryl and aveeno lotion. Just when I think there going away, they keep spreading. There are no other symptoms other than the itchy bumps. My other two children don't have any bumps or symptoms. The two with the rashes have eczema but these look like chicken  pox or something. They are current on all vaccinations. Is this a mild case of chicken pox? There's no oozing. Just medium size bumps that become small with a scabby pointy tip. Help. I've made an appointment for them to see their physician. What are the possiblities? Detergent? mites? measles?