Ex and child safety worries

[trickyex]

I posted this in relationships but didn't get much response so am posting here as well....

I am recently divorced and am struggling with my ex. He was very controlling while we were together and is very difficult to deal with.

He regularly asks to change access arrangements for our DSs who are 10 and 7 and so far I have tended to agree, partly to avoid conflict and also because I always did fit in around him when we were married.

But I am very worried about holiday arrangements this summer and am really at a loss about how to deal with it.

On past trips abroad (he has taken the DSs away before) he has left them on their own in hotel rooms (for short periods) and, most worryingly, left them on their own in a hotel pool. I only found out about this from the boys, who told me when they got back, as they had been told off by a hotel staff member (the pool has no lifeguard, DS2 was 6 at the time and a weak swimmer, not wearing armbands).
Ex also forgets to use sunscreen which has resulted in DS2 getting sunburn on his face.

I also have concerns about ex accessing porn on his ipad which the DSs use, he doesn't wipe his browsing history and the DSs use the ipad unsupervised. I have raised this but I wasn't happy with his response.

ExH wants to take the boys abroad for a two week holiday this summer to a villa offered by a friend, he will be there alone with the DCs. I have no idea about the villa location/layout/pool and am worried about my ex's tendency to disappear off for a fag/have a few beers at lunch time and the obvious risks to the DSs' safety.

I raised this with him on the phone recently when discussing holiday arrangements and he laughed at my concerns and told me that I had no need to worry about the pool issue as DS1 is a good swimmer....

How can I best deal with this? Any advice would be much appreciated.

[STIDW]

Persuasion tends to work better than blame and the imposition of rules. So the first thing is to attempt mediation to see if any agreement can be reached. If so the terms of the agreement and any conditions can be written down in the form of a parenting agreement. Parents tend to stick to such an agreement.

[trickyex]

Yes I agree STIDW but when I suggested via email that we go to mediation or counselling he ignored me (not helped by his being a lawyer and he knows the local mediators....).
I will try again.