Scotland visit -
There is a huge difference between the two choices. Glengoyne is on the outskirts of Glasgow and can be done easily because it is near the center of Scotland.
The other three are located on Islay , a long drive because of location of the ferry to the island. Ardbeg, Laphroaig, and Lagavulin all are located within a mile or so on Islay , not far from the mainland ferry. Because of the tour times, it is difficult to get to more than two Islay distilleries in one day, i.e. a morning and afternoon tour. When I visited Lagavulin, it was an unusual experience to be downing the peated monster at 10:15 a.m., but like they say, it is a tough job and someone has to do it. I think the brief stay in Scotland rules out a long drive to and from the ferry to Islay and the time on the ferry.
Glengoyne is a nice suburban setting that will take only two or three hours out of a four-day stay in Scotland . It is a nice setting on what formerly was a farm; the tour is well done and costs about 4 pounds. To my knowledge there is no other distillery close to Glasgow.
The best source of info is a book entitled Visiting Distilleries by Duncan and Wendy Graham.
Also, an easy distillery tour if you will be near Edinburgh is Glenkinchie distillery located only a few miles south of Edinburgh. I had a great distillery tour with a seemingly endless dram at the visitorís center, followed by a tour and even worship service at Rosslyn Chapel (about five miles away), made famous by the book and movie Da Vinci Code.