I think CiviCRM would work well for your needs. Obviously, you wouldn't need to use every feature. In combination with a Drupal, Joomla, or WordPress site, you could have a signup form for new members and events for each hike. In Drupal, you could use Views to display upcoming hikes, or in WordPress, you could use the CiviEvent Widget plugin (shameless self-promotion).
It's simple to see what hikes someone has participated in, either on their contact record or in flexible reports. It's also straightforward to give multiple leaders access to administer the system--unlike other systems that charge extra for each administrator.
One note: in CiviCRM, the word "member" is used for someone who pays dues to get a membership that has a fixed term. (There are free memberships and lifetime memberships, but those are generally used alongside paid and/or time-limited alternatives.) Many organizations consider "members" to simply be people on the mailing list. If that's how you all use the term, you can simply ignore or turn off the CiviMember features.