Narita Airport station is accessible by elevator.
Chiba station has escalators from platform to concourse level - http://www.jreast.co.jp/estation/stations/989.html
Mobara may require you to climb some steps.

These stations are not "monsters" like Tokyo (which can be challenging to navigate). So it should not be an uncomfortable journey - even with some luggage.

Still... I like driving around the Japanese boondocks....