Exciting!!! Yes, I think everyone should plan a spontaneous trip at least once
Actually, back in 1995 B.C. (before children) my DH (then DBF) and I decided spur of the moment to drive from Flagstaff to Anaheim. We started at about midnight, got to the gates for park opening at 8, spent the day and then turned around and started driving back to Flag at about 10 p.m.
I did have a scary moment when it was my turn to drive and for a moment, I fell asleep at the wheel

Thank goodness for those bumps they had on the side of the road. I had to pull over because I was so shaken up that I could have actually killed us. We did have a really fun time though.
Of course, now we have 4 kids ages 7 and under. I have to plan at least 2 weeks in advance just to make a trip to the grocery store!