Cindy, here's what comes to mind:
(a) adults say they want to be treated as rational equals; actually, in groups, they need to be treated more like high school students, only partly responsible.
(b) take no small measures. You're going to have to use a stick to get anything going at this point; your approach may sound good, but the results are flat; you need to put a spine in the team: no such thing as a team of equals, and no such thing as being a leader without also running the risk of being disliked;
(c) Boy Scout definition of leadership is "getting the goals accomplished while keeping the troop together."
(d) what would be wrong with tossing out the lackadaisical ones, keeping the hard workers? I think in the end, people need some kind of assignment or personal mission in these situations; you're going to need to spark some personal motivation in folks.
i got a feeling i won't like playing on your team....
apparently you are a type who believe more strongly about what you think the team's goal should be, rather than team's goal as a team. it is apparent in Cindy's case that goal vs real life priority mis-match is the reason for what Cindy describes as "not working".
don't need boot camp methodology in (most) adult league tennis.
oh.. yes - i have been part of teams that went to sectionals (and did well). and yes, my last 3 yr match record is something like 32-4 (all in singles).
so i don't need my captain to "spark some personal motivation" or "treated like high school students"