Well, you can go with him (yes, yes, I do remember how hard it was when he visited with your hearing ability being tested and all).
It usually is a straightforward process. And that way you can process the car simultaneously (IIRC, he has his car up in Canada).
Go to the US, get your passport stamped (some POEs prefer it) and pick up car export documents (don't forget to send them/fax them ahead of time depending on the POE - you can do it way in advance so you don't have waiting time after getting CoPR). Tell them you want to return to Canada so you can u-turn.
Cross over the bridge to return to Canada, tell the Officer you are landing, s/he will give you a slip, go inside. Once inside, tell the Immigration Officer you are landing and hand over slip from outside officer along with passport and CoPR. Also advise officer you have a B4 form too. The officer will confirm address for PR Card and ask a few questions to probe for changes to marital status, dependents, etc and to confirm all the info on the CoPR. Then officer will ask your husband to sign his CoPR and the officer will stamp and sign it too. That's it for immigration.
Then, officer will direct you to Customs Officer to process B4. You let them know you just landed and hand over B4 form. They will read through it and stamp each page. Send you over to cashier to pick up your receipt and give you the stamped copy back. Since you are importing the car simultaneously, you'll need to fill out the RIV documentation that you'll need for registration also and your title.
Take a look at http://www.canadavisa.com/canada-immigration-discussion-board/leaving-the-us-to-land-in-canada-in-16-days-anyone-have-time-for-a-onceover-t105182.0.html;msg1474430#msg1474430 for the car specific instructions.