I am be no means experienced but have always been told to not force the issue on coats just to make them look like an adult before their time. In the puppy classes you'll have a range of those with little coat, those with masses and the ones who've been able to strip some and start looking like the business.
However, bare in mind that they could also be in the top end of the age bracket and that month or so makes a difference too which the judge should take into account
Good luck at your first show - don't forget to post results