I'd make it shorter, like about 5 miles, for your first trip. In other words, I very much agree with Glenn and Bill. Remember, also, the days will be shorter. The first few times out, you want to camp early enough that all your chores are done by sunset.

Hopefully you will already have tried out your gear in the back yard, putting the tent up and down several times, cooking with your little stove on the patio, even sleeping out there overnight. Camp routines will take a lot of extra time your first few trips anyway; you definitely don't want to be trying to set up the tent for the first time on a dark and stormy night with instructions in one hand and flashlight in the other! If you can't do this ahead of time, definitely do the car camp/dayhike routine for your first trip. And, as I said above, camp early so you have plenty of daylight!