Ground transport for children in California

We’re flying into John Wayne and need ground transportation for 2 groups of people flying in at noon and 4:00 pm.

Each group will have 5 adults and 4 children, ages 1, 3, 5, 6.

We can’t bring car seats with us and we don’t want to rent cars because it’s slow and we’re not planning to leave the Disney propert., what’s our best option for ground transport?

We have a quote for $600 for a 10 person sprinter van shuttle. That would be $2,400 for the 4 trips we require. Seems kinda pricey. Do we have any better options?