This situation is how I feel whenever a friend wants to use me as a knowledge base. The biggest thing is letting them know you dont even have all the answers for your own cycling life let alone theirs 
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I always tell people if you want me to go to the shop with you I will but unless that happens it will be hard for me to be a 3rd party assistant.
But like others have said you’ve handled it well enough up to this point. I wouldn’t overthink it too much and just let them figure out what kind of cycling stuff they like to do and continue being a good cycling buddy and friend