AC 21 rule allows H1 portability. ie. you can start to work in company after sub-mitting your H1 petition.
By strict interpretation of the rule, yes, you will need to stop work once capped H1b is approved. However, in practices, CIS would have difficulty to monitor this. (read lawyers' announcement in MIT-bbs.or search my post sometime between dec 07 to feb 08).
In addition, if I used EAD. What the status of my son will be ( current with H4)?
Is your son AOS too? Then he is AOS. Otherwise, he will lose H4.
