Parents: Beware of Avis... They don't care about the safety of your kids

I had the most frustrating and scary experience with Avis tonight. We are preparing to take a trip to South California at the end of next week, where we will have our 2 young kids (3.5 and 1.5 year olds) with us. My in-laws will be coming with us as well, they were the ones who made the reservation for a car with 2 child safety seats, from Germany. Through the process, someone had suggested that it might be helpful to confirm that the car seats were really going to be available when we come to pick up our car. I thought it seemed a little but unnecessary since the reservation clearly stated that they had reserved - and paid for - 2 car seats. But to appease everyone before the trip, I went ahead and called Avis.

OMG - What a scary experience. I talked to 3 people, including the shift manager (Andrew Diaz) and got told that Avis can not guarantee that we will have car seats when we come pick up the car. Even though, it's written in our contract, they might not be able to fulfill their obligations at the end! Apparently their systems can take the reservation, but they don't sync up with their car seat inventory. And, these 3 agents were able to tell this to me in a straight voice, without blinking!? There are so many wrong things with this.
1. How hard is it to build a system that tracks car seat inventory? They have to know how many cars they can offer. Can't they do the same for car seats?
2. More concerning, they don't seem to care about breaching a contract that they let customers get into!
3. And most concerning, they don't care about the implications of not having car seats available for parents who need them to drive away from the airport. When I asked Andrew if I might have to drive my kids without car seats if Avis can't provide them, he couldn't deny that possible scenario. WOW! I see a huge legal liability in Avis' future if this policy gets exposed.

Really, Avis, is this what you stand for? Not caring for kids or for the law?
Sadly, it seems that it's not the first time that customers have horrible experiences with Avis and their ignorance of car seat safety rules
Is someone in their Legal department aware of this?

Sadly, we can't wait for the pending lawsuit to happen. I think we will probably just cancel our reservation (since Avis isn't able to fulfill their side of the contract, this shouldn't be too hard anyways).
Does someone know any good rental car agency that is reliable with car seats?