A follow-up:

Using the same agent a few weeks ago, got a car service at a reasonable (if high price) to pick up at LAX and deliver to a relative's house, and back again. Service was expensive, but not extraordinarily compared to an Uber XL. Actually glad we locked in our various car services at LAX and also SEA and YVR, as I'm reading reports that Uber drivers are hard to find and gas prices are rising, etc.

One last thing, our agent was able to get us written confirmation of the outdoor seating (see above post).