We love Lancaster and try to get there twice a year. Two of our favorite places to stay are Bird In Hand Family Inn and Amish View Inn & Suites. They are both located on Rte 340, Bird In Hand Family Inn is right next to the Farmers Market and is a clean, quaint place. The rooms have mini friges but no microwaves. There are however microwaves throughout the buildings in the laundry rooms for your use. There is a restaurant attached that has a great buffet for breakfast, lunch and dinner as well as menu choices. They have an indoor pool as well as outdoor. The grounds are very nice with a mini golf course, playground areas and they offer a bus tour of the Amish country. If you were to stay here, you would want the "Pool Building" as the other building is an old motel style unit which I have found to not be as clean and not convenient.
Amish View Inn & Suites is adjacent to Plain & Fancy Restaurant. They overlook an Amish farm and schoolhouse. Their rooms vary in size and ammenities depending what you want. We have stayed in a double and a king and they were spacious and had both frig and microwave. They include a full breakfast with a large assortment, nightly snack and coffee available in the lobby. They have a "Great room" where they show a nightly family movie and offer board games for your use.
Also while you are there, check out if there is a production going on at the American Music Theatre. They have wonderful shows!
We have also stayed at Willow Valley and it was great, however it is not centrally located to the heart of Amish country.
HTH!