Robocars most certainly exist. They’re probably about 5% of car traffic in San Francisco. I’ve not taken one yet (taxis/ubers/Waymos are mostly impractical with a young kid in the US as you must use a car seat unlike in most European countries) but as a pedestrian they seem mostly a safer than other drivers. As a driver I expect they will eventually induce gridlock but the city can always create more bus lanes.
Portable booster seats are pretty small. I can’t see it working if you have a kid younger than the booster seat min though. Only a few states have strict rules here, Washington and California being a couple, although I think California has a taxi exemption.
Robotaxis ≠ robocars.
The robotaxis that do exist only do so in very limited places using very expensive technology (including off-shored service center for intervention) that is not available for the public consumer markets.
How old is your kid? In which European countries do you think the law does not mandate child seats ?