Always a tough situation, and a lot of factors to consider.
Bottom line though is that Coach needs to set the tone and set down the expectations. If players don't follow along then they have left themselves exposed.
Our team takes things VERY seriously "in-season", and while we play year round we are a little *** with the off-season due to multiple high school sports participants, and maybe most importantly we "KNOW" that we have kids working year round with instructors and making most of what they can. In the end, we KNOW that "they" will be ready when it matters, so that "we" can be ready as a team also. In return for their outstanding dedication, we encourage them to enjoy a full teenage life, and happy experience overall, and stay "fresh". It's a balance, with some mutual trust involved, but that trust has been earned also, from past behaviors.
This wouldn't work for us if we had the wrong kids/families for our system. so, again, in my mind it boils down to setting expectations, having rules that apply to your own situation, and then executing the plan.
Like a few others have stated, make known what you want, be clear, then be judgmental ... if/when needed.