-Because they stamped the H-1 and H-4 for you and your child, respectively, your status is still H-1 and your child is still H-4. Because you and your child returned to US within 30 days from Canada, you did not need an H-1/H4 visa and just used the I-94 to enter US even if you showed them your AP (the officer did not considered you to use AP in this case). You do not need to do anything unless you stayed in Canada for > 30 days at that time before you returned to US.
Not the control number. The visa# is the number in red color on the visa.
My reply: Yes, I found the visa #, but it was before I got AP. Guess it is not useful?
-You need to put that visa number (see above).