STT to St John with car seats

We're traveling to St John next month with two kids under 4. We'll be flying with two travel car seats, anyone have experience taking the taxi vans from STT to Red Hook? Are drivers open to belt installing car seats in the van with other passengers?

On our last trip we just had one little one and hired a private taxi from STT to Red Hook, that ended up just being us in a van to ourselves though so it felt a little over kill.

We've already rented a car on St John so renting in St Thomas and taking the car ferry over is not really an option.

Thanks!