One thing I would say about killing them with kindness though... There's kindness while still adhering to orders (and expecting the other side to adhere too), and then there's the sort of kindness that the other side takes advantage of, where concessions are constantly made to avoid conflict. I would say there are certainly times where you need to be firm and if that requires something less than kind to be said or done, so be it.
In my case, I currently have orders that for the children's birthdays, the children can spend the day with me if I'm not working, or the evening if it's a work day. There's nothing in the orders that say the same for my ex, who is the primary carer and has the majority of time/care with the children. It turns out this year that my daughter's birthday fell on a Saturday that was 'my weekend' with the children: Saturday morning to Sunday afternoon once per fortnight. My ex emailed me, assuming that since I have an order that provides time for me with the children for their birthdays, that it would and should be reciprocated and that she could keep the children for the entire Saturday. She asked for my confirmation that I agreed with her handing them over at 5pm Saturday instead of the usual 10am on Saturday. Now, I agree that our children should be able to see and speak to both parents on their birthday. That's how it SHOULD be in any normal split family.
But in my case, only two months earlier on Mother's Day (which the orders say she is to have Mother's day Eve to Mothers Day with the children), it fell on my weekend with the children and I lost the only overnight time that I have with the children each fortnight, meaning I effectively went a month without any overnight time. I tried to negotiate an overnight on another Friday instead of the lost Saturday as a catch up (for other reasons, I had to give up another weekend day with the children around that time so by then I was down two weekend days and an overnight) and my ex refused to consider any of my quite reasonable proposals, selfishly stating that she would "prefer to stick to the orders". This is just one of many many situations over the last couple of years where she's proven herself to be selfish, trying to restrict my time with the children whenever possible. So, when the time came for me to decide whether to extend kindness and give her some of my limited and precious time with the children or "stick to the orders", I chose to follow the orders.
Long story short, my advice: Don't give them any ammunition to use against you (be polite, as unemotional as it's possible to be under the circumstances etc), but don't let them take advantage of your 'kindness' either.