solution that we have used multiple times on drives from CA to UT. You can get headrest mounts for iPads off of Amazon for not much ($20) and they hold the iPad or any other device securely. From there you can either put the sound via Bluetooth through the car speakers or you can connect via Bluetooth to headphones the kids wear.

It’s nice because you can get the screen up so they aren’t staring down at the lap for infinity hours which is pretty brutal on their head and neck. It’s a very easy workaround to not having the entertainment system in the car already, which i assume a rental would not.

Here’s one of them that we have used - and a Prime Day deal, how about that:

Macally Car Headrest Mount Holder for Apple iPad Pro / Air / Mini, Tablets, Nintendo Switch, iPhone, & Smartphones 4.5" to 10" Wide with Dual Adjustable Positions and 360° Rotation (HRMOUNTPRO),Silver https://www.amazon.com/dp/B0148WQKNQ/ref=cm_sw_r_cp_api_glt_fabc_W4R3C3R7TTMXZF3PB8D1