I really don't think it will be a problem if your few minutes late. Do u have cell phone that you could call dining and let them know your on your way. I'd try to get in the park about 3:50, and let them know you have ressie in CRT maybe they will go ahead and let you in or at least one person in your party to go check in. If you have confirmation printed out, then you can show this to CM at the gate, might help!
I've also heard some people say they got in before 4.