I completely agree with ladyjbug. The parents' reaction to this issue would be a challenge for me. If I have explained to you what the situation is, told you WHY I need things to be a certain way, and you shrug your shoulders at me and say "Oh well".... Hmmmmm.
I am not an advocate for "my way or the highway". I understand that not everyone is going to parent the way I do, or think the way I do. If I only worked with those that I COMPLETELY agreed with when it comes to methodology..... well, I would be empty, hahaha.
But it is important that you and the parents are working as a team, and that your core beliefs are the same. This may end up being a dealbreaker.