---- I think you have only H1 and H4 approval notices or extension filing receipts ( Approval Notice, filing receipt is NOT VISA). You are writing VISA renewed? Did you have valid Visa stamp in your passports???
so all we have are the I-94's (good until 2006) which are still attached to the (pre-transfer) H1 and H4 forms.
---- It seems you got H1 and H4 extension approval notices with I-94 extended from USCIS and never sent your passport for Visa revalidation to DOS in USA
So we don't have any *stamps* per-se -- are the attached I-94's all we need (even with the original H visas we never got stamped -- we simply stuck the paper I-94's into our passports and I think that for trips of less than 2 weeks or so into Canada they don't bother with new stamps)?
------ That is 30-day rule called Automatic visa revalidation for visits to Canada and Mexico (to reenter US with same I-94). I don’t know your country of citizenship, for many country citizens the automatic visa revalidation does not exist now. Go to department of state site and search for “Automatic visa revalidation) and take the print out and read if you qualify to use that. If not qualified you need H1 and H4 VISA stamped in your passports to renter US from visit to Canada or Mexico
My main concern was whether we need to wait until we get something else back from the USCIS first but I can do as you suggest and bring the Receipt Notice for the H transfer with me (along with any other records).
----- You both have got H1 approval and H4 approval notices from USCIS or just filing receipts, what you expect more from USCIS? If you have just H1 H4 filing receipts then USCIS will sent you approval notices.. USCIS does not stamp Visa sticker in passports. If you don’t have Visa sticker till the validity of your H1 or H4 extension or I-94 dates you can send your passport for Visa revalidation only if your Visa stamp in not expired more than 1 year. It takes 3-4 months to get passport back with Visa stamp from DOS in US
Visit:
Visa Revalidation
http://travel.state.gov/hlop.html
http://travel.state.gov/revals.html
*** Check your passports and look at VISA stamp. On what date the Visa stamp in passport expires. From your post it is difficult to make if you have valid Visa stamps in your passports