If you can get a taxi van it would be a $40 flat rate, at least one way, but I'm not sure about the availability of the vans. Maybe you could call the airport and ask.
Super Shuttle would be $80 for a group of six, not including tip; they can do a private van for you for $90.
You might be able to get a private van service for less, but I'm not sure who would be good for that. Maybe your hotel has a list of possibilities.
You can splurge a bit and get a limo for not too much more than a private van. We did this for our family of 5; it was $90 each way; but in reality with taxes, tip and surcharge it came to more like $130 each way. Still, pretty fun to pretend you're a rock star on the way to
Disneyland!
I'm thinking your hotel should have some good suggestions for you of reputable transportation firms. Maybe give them a call?
Hope that helps!