It sounds like you pretty much have everything covered. Frankly, you'd generally qualify for a VR allowing you to remain for the duration of the process at this stage, but you're just trying to visit. You should bring a copy of the sponsor approval letter along (in case they start asking you questions) but I'd expect you won't need it.
Just think about how you want to answer the questions they might ask you - what is the purpose of your trip to Canada, are you bringing anything with you that will remain in Canada. So rather than say "I'm bringing my daughter to see her father's family" you might just say "I'm bringing my new daughter up to see her grandmother". Both are true statements, but the latter leaves less for the BSO to question - he's not automatically going to think you intend to overstay on a visit to grandma around holiday time.
If the BSO sends you to secondary, you can explain further your circumstances - that this is your daughter, and you want to show her off to grandma and the rest of the family. At that point the secondary officer may ask about your daughter's father, etc. That will lead into the PR side of things. As I said, you'd normally be able to get a VR for 6 months (which is what you get when they let you in without a date anyway) and stay in Canada with your husband while they process the PR application, so thinking you're going to overstay is a bit ridiculous at that point. BUT, if you are still very concerned you have two additional things you can do: (1) you can show up at the border during working hours. Then a suspicious secondary officer can call CIC and get a real person if that's what he wants (again, I note that this is so unlikely...). And if THAT fails and they decide to turn you around, you can ask for a TRP right there at the border - and I say this with the firm belief you will never get anywhere near this stage and in fact I suspect you'll spend more time worrying about it than the actual border crossing will require - in the "early admission" category. You have your sponsor approval letter. If you have a copy of your FBI clearance letter, bring it as well (even though it will say "unauthorized copy" all over it). TRPs are used to overcome inadmissibility and there is a special category for sponsored spousal applicants who are just awaiting routine processing. Absent any evidence of criminality (hence the FBI letter copy) that's all you're waiting for.
Ideally, I hope you get your COPR before you have to travel - then you can spend those 15 minutes in Secondary becoming a permanent resident.
