As a person who used to ride public transit (busses and trains) in LA and encouraged people to use it, I would absolutely avoid anything MTA related. It's gotten so bad in the past 5 years that even members of the County Board of Supervisors admit it's dangerous. I think two bus drivers have been stabbed in the past few months. Multiple incidents on the trains have happened in the past 12 months. The metrolink is still safe but that is a regional rail that won't take you to the places you want to go. It would be useful if you wanted to travel between Sherman Oaks (Van Nuys station) to Disney (Anaheim station). The train to get you from Sherman Oaks to Universal is the red line (MTA) which is dangerous and at the very least your kids will see some disturbing shit. It would be very convenient otherwise which is very unfortunate that it's in such a bad condition.
Bite the bullet and rent a car. If you're not familiar with Turo it's a great app that's essentially AirBnB for cars and you save a considerable amount of money. You can even have the person meet you at the airport for an additional charge. No rental counter etc. I use it all the time and never had a problem. If not, you can always Uber to an offsite rental car company instead of using the overpriced airport locations. I do that too quite frequently and save money. If you're going to be traveling long distances frequently then Uber is probably not going to be cost effective.
Over the last 12 months, violent crime reported by the Los Angeles Police Department on Metro properties increased 14% to 16% higher than pre-pandemic levels.
abc7.com
EDIT: Hop on hop off tourist busses are completely different. They are likely safe but I have no idea where they go and how efficient they are.