my wife and I have had all the same interviews and they have been on the same day, but if we were not in this together I would definitely be going by myself.
At KCOM your spouse/kids can come with you and while you are being grilled (just kidding!) they go off with a member of the SAA (student associate's axillary) and check out the town, get to know some of the other spouses, etc. I would strongly suggest bringing your spouse with you because your decision on where to go to medical school will affect your entire family.
I would find out what is considered acceptable at the specific school. It is a great idea, but I have heard that it is considered very poor form at some schools. An alternative is to schedule a tour that is not on the interview day with a student ambassador for a less-formal setting.
My father usually travels with me for some quality father-son time since my wife is too busy with clinicals. He usually does whatever around the town while I'm at the school. Traveling alone would really suck.
If I flew, it would be just me. However, I'm too poor to fly so I always end up driving.