Lancaster was my mother's home town, I still like to go and visit. There are lots of things to do and see there. The touristy stuff is all on the northeastern end of the area. Harrisburg is the closest airport. For things to do and see, you might want to check out PaDutchCountry.com as that is the tourist board website for that area. There are lots of B&B's and you might be able to hire a driver to take you around if you aren't comfortable driving.
May is a good time of year to go, as spring in central Pennsylvania is just lovely, lots of flowering trees and shrubs.