I already think I know what needs to be done but Im posting in case there are any other options.
For some background, when together my ex and I would always argue about her not wearing her seatbelt (to the point where I would refuse to drive until she wore it while in the car and we'd sit and argue for 20 minutes waiting). Even after her crashing on a dual carriage way at 50mph, headbutting her steering wheeling and splitting her mouth open she still is very relaxed about wearing her seatbelt.
Obviously she can do what she wants now but a few weeks ago, when she was picking up our 8 year old, I noticed that when she got in the car my child, along with my ex's other child (3 years old) only had the bottom part of the seatbelt on while sitting in the front seat (it's a van so has 3 front seats). I saw my ex put the seatbelt on my child and put the shoulder strap behind her. I called her out on this and she flat out denied it despite me saying I saw her do it. We even asked our child if it happened and they said yes but only because the other child always does it.
Once again, today I've caught her not even putting the seatbelt on our child (or the other child) while leaving my house. I recorded this and have video evidence as clear as day.
I think my only option is to flag with the police but as you can imagine this will completely destroy any civil relationship we have. I don't see what choice I have though as I know my ex doesn't care for seatbelts, and I've already raised this once and was lied to about it. Are there any other options though? I suppose my worry is I report this, the police do nothing and she continues to not put seatbelts on the children - atleast in that scenario I know I've done the right thing.
Any advice?
I am not too sure what to suggest? Maybe call 101 or use the police chat service online to see what they say or maybe cal children's services and see what they say about it. If you havent already, drop your ex a polite message explaining your concern so at least you have proof you had mentioned it before. It is a massive risk to the children so it should be stopped.
I would say you definitely need to do something about it, aside from the massive risk she is taking with the children now, she's also instilling this behaviour into them for when they are older.