There are two parts to H1 extension. One is the approval of new I-129 the actual H1 petition and the extension of status. In your case even if you leave the country the only thing you will abandon is the extension of status. But you can use the new petition (I-797) to reenter or get a new H1 stamped, in case od dependents they do abandon their application altogether but they are still fine, as they can get a new stamp based on your H1 (current valid till My 2008... or extended petition).
In your case if you get back before the approval comes using the old stamp you will have to file for extension of status for all of you again. you cannot use the I-94 that comes with the approval.
Otherwise you are safe.
I hope your mom recovers and does well.