Hi Miriam,
Unfortunately the current version of Little Math doesn't have a feature for creating individual "child profiles" like what you described. In the meantime, what you can do is try to take note of which lesson each child is at in a diary or calendar. If you have two computers you may opt to use PC 1 for LM with the younger child and then PC 2 for LM with the older children (since LM can be installed and activated on up to 2 computers).
I hope this helps somehow!
