Lancaster PA is probably the largest Amish area but I've not been there so I'm not sure what tourist stuff they have.
There is also a large Amish community in Iowa - Amana Colonies. There are I think 7 different villages, all have at least 1 shop, all have quilts <g>, the largest community has a lot of shops for arts, crafts, food, etc. - and of course the Amana manufacturing plant. Very strange - this big Amana "radarange" mfg plant right there in the Amish village. Haven't been there in years. It's a "day" trip, you won't spend much more time than that there.