If you ever get the chance you have to do this tour. We did it at our own pace and had a fabulous time. The kids loved scrambling around in all the nooks and crannies. Hubbie loved the history and I just enjoyed the whole experience. We took 2 or 3 days and visited other places along the way.
Of the 4 sites my favorite was Jedburgh. The others, Kelso, Dryburgh and Melrose ran a very close second :)
The four abbeys were founded during the reign of David I and were basically a gesture to the English "come get us if you dare" type thing. They did dare and the abbeys were at the center of many a border battle. Today all 4 are very beautiful ruins with lots of little surprises to discover.