It's been a few years (last crossing was 2008), but the best time is late evening, and using the Ambassador bridge. The extra drive up to Port Huron turns into a wash with crossing time. It'll take you longer to drive out of the way than you'll save just taking I-94 to the bridge exits.
Advice from somebody who has had clear sailing across and severe searches;
Rental cars might not be permitted. Check your policy with the rental agency... This has been my #1 no-go for visiting my friends in Ontario.
Keep the car semi tidy. The more crap your car has laying around, the more likely they are to search you.
Be specific with destination and duration. If you sound confused or unsure, they will have more questions for you. This may lead to a search.
Get a note for all minors. They made a huge deal about this when I crossed with my brother when I was 18, him 17. I mean a giant deal.
If they address your daughter, let her answer. They will only get mad if you speak for her.
Don't mock them when they say "Eh!?".
If you can find one, drive across with a hearse. Fastest crossing both ways I've ever had.