generally these kinds of rashes may occur in a variety of viral illnesses that may pass off without giving any trouble. and many do not cause any treatment at all.
these lesions do not need any specific treatment other than symptomatic like if there is itching, to make them resolve as they resolve on their own.
this seems to be contagious as this has infected both of your children simultaneously. likely they got this infection from some common source simultaneously.
there should not be anything to worry if your children are immunized against common viral infections like measles
etc. but you have to be careful to development pf any other symptoms like high grade fever, refusal to feed , lethargy
or irritability, bleeding from any site etc.
to be sure you can consult your pediatrician
to take his opinion as he would be in a better situation to judge things better.
wish your children good health
Dr. Amit Kumar