I second Inveraray and the George, absolutely. About an hour and a half from Glasgow (although RyanAir will probably drop you at Prestwick, another half-hour the wrong side). If you stay two nights there, you can visit the beautiful ruin of Kilchurn Castle (see below) on Loch Awe, and see a great variety of antiquities (chambered cairns, standing stones, medieval grave slabs, etc.) in Kilmartin Glen. You might even make it up to Oban, although I imagine the distillery tour is a fairly standard Classic Malts one...I haven't actually done it.
Another possibility is Arran; the ferry from Ardrossan to Arran is not far from the airport. The distillery there is only about ten years old. There is also a brewery, a ruined castle at Lochranza, and a number of standing stones and such on Machrie Moor. Good walks to be had, including an ascent of the Goat Fell, if you are up to it. You could even do a circuit including Arran and Inveraray, if you have the time.
Finally, from Prestwick it's not very far to Scotland's deep south, Dumfries & Galloway. I am myself looking into staying in Isle of Whithorn when I go in October; I've never been in that corner of the country, but it looks like there are a lot of interesting things down that way. Bladnoch is very close by.
But again, I echo Admiral's recommendation of Inveraray and a visit to Loch Fyne Whiskies (your wife can visit the woolen shop down the road if she's not interested in watching you drool for an hour). Splendid Highland scenery, for so close to Glasgow.
Check out the Undiscovered Scotland website (http://www.undiscoveredscotland.co.uk
) for information, travel tips, and a fair selection of accommodation.
Kilchurn Castle--photo by Mr Tattie Heid