I won't stop him as it's ultimately his call and I trust his judgement but boy is it making me feel on edge. For context, he's a great father and were still mostly working really well as a team.
Ex comes from a fairly dysfunctional background but hauled himself out of it via education and moving to a new city. He is NC with his father and only sees his mum occasionally (they're divorced and are NC with each other too). I stopped engaging with all of them years ago as can't abide drama llamas of any description.
The whole set up with his mother (and half sister) is shambolic. No-one works, kids running riot, un-toilet trained and un-neutered dogs toileting inside the house (and being left for very long periods) and getting pregnant. Ex MIL rarely contacts ex except to ask for money despite having no shortage of luxuries. Ex's half sister has two children. His mum does more of the parenting than his half sister (the DC live with his mum). She (Ex half SIL) seems to have spectacularly poor judgement and a warped sense of priorities and has gotten romantically involved with not just one but numerous weapon wielding, drug dealing, psychopathic criminals. Because she likes the trappings and glamour of being a gangsters moll. After a split with one such catch, ex-MIL has been suspected of talking to the police (no idea if true or not) and her house has been attacked more than once. The last attack left it inhabitable (no-one was home, it would likely have resulted in fatalities if they had been). Ex MIL and SIL have now been moved half way across the country by the police. Into hiding. The kids have been separated (they have different dads and have gone to their respective families).
Brief interlude while I sing 'My Way' by The Sex Pistols and tell you that contrary to what you may be thinking, I do NOT live in a soap opera. This is so far removed from my naice middle class upbringing and life as it's possible to get. I fucking hate my kids being connected to this kind of lifestyle.
One of my many 
faces at the minute is because this location has changed four times in the last fortnight.
Ex is meant to take our DC for a visit tomorrow and the location has literally just been changed again. To a location 50 miles away from the one before.
They don't see his mum all that often anyway but when they have it's always been at her old house. I'm beyond dubious about what kind of house they will be visiting or what they could be exposed to.
Am I being precious?
Gin for everyone who made it this far btw.