Disabled friend who can’t keep up.

This ‘subject’ sounds very selfish, but kindness is really what my question is about. We are a group of friends, all widowed and in our late 70s. We would like to enjoy day trips and outings together, mainly by coach, shopping, visiting historic houses and cities. But one of us has become very slow and cannot walk far. She doesn’t use a wheelchair but is always keen to be included, not realising that everyone is restricted when she is. We would hate to hurt her feelings, don’t want to arrange adventurous outings behind her back, but feel that we are between a rock and a hard place. Are we being selfish? How can we resolve this? Advice please…..