There are opportunities which Uber isn't in a good position to tackle simply because they don't capture many trips made by 8 to 16 year olds (kids alone in car with an unknown driver is scary to many parents); and these trips frequently involve being at a common place at a common time with their peers (sports practice/games, band/scouts/clubs, school, etc.). Parents will almost certainly stop being a chauffeur to the kids in their neighbourhood (many already trade-off carpools to kid events) and let Waymo pick it up, especially if the passenger cannot change the destination.
Once they start competing for growth (long after basic taxi enthusiasm has passed), I expect recurring kid trips to be viewed as a very important market for the same reason banks pay close attention to 18 year olds. Capture a 12 year old customer and you'll likely have them as a customer for decades.