Little bit late to add to this post but I am recently turned 19 myself and I have went to Leeds fest 2022 and 2023 when I was 17 and 18 respectively. I can confirm that there is plenty that goes on at the festival which can get your children in trouble, however, 99% of the people that go are just festival-goers who just want to let loose and enjoy the music.
In 2022, there was major safety issues, from a kid overdosing and passing away to the final night which I could only describe as purge like, explosions and fire everywhere the poor security guards were rushed off their feet.
Despite this we went back in 2023, and it was like night and day. The security had increased tenfold. everyone was thoroughly searched and drug dogs were out in force at entry. From personal experience the amount of drugs was significantly decreased and the final night was actually quite pleasant. There was not one fire in sight, I was reliably informed by my dozens of friends there that it was the same across the entire sight.
Overall I would highly Leeds fest. The music was great. The people are great. The experience was great. Only thing I would recommend is bringing a trolly of some sort to carry all your belongings, that walk into the camp is long, hard and painful and a trolly makes life so much easier.