Personally, I'd start with the classic, beechwood-smoked rauchmalt. If you're looking to be subtle, probably not more than a couple pounds. If you just want a hint - maybe a pound, pound and a half.
For "sweet", use a fair amount of a medium crystal malt, upwards of a pound. Could probably get more like a pound and a half (maybe split between some 40 and something a little darker), I've heard of people going north of two pounds but that's pushing it. I'd probably go with ~0.75 of C60 and about the same of 80L, or some combination. Lighter crystals are more pure-sweet, medium (60-90L) more caramel or toffee, darker ones (north of 90L) get more dark-fruity (good but maybe not for this beer).
Munich malt's another real nice complement in both smoked beers and in Amber ales, gives a deeper maltiness and a little toastiness (not sweetness, that's why you need the crystal).
Whatever you do, avoid peated malt, that's a harsh, acrid smoke (kinda like licking the inside of an ashtray) that's the exact opposite of what you want to accomplish.
The only reason I'd caution against smoking your own is that it's a little more difficult to control the amount of smokiness. Using the rauchmalt at least for the first attempt is a way of getting a fairly known, consistent level of smokiness (assuming the rauchmalt is fresh).