I actually arrived at 9:30AM. We were told that they may not ready to accept new luggage, but they took it after waiting only a few minutes at the curb. I made it back in the rental car shuttle by 10:30 and met my family waiting in line in the garage the over pass. We start entering the port together by 10:45. We were in boarding group #3, so some people arrived even earlier.
I can't guarantee if this timing will work for you, but will try this again on my next cruise.