You really have 4 options:
1) Mears - costs $12 per person round trip
2) Taxi - costs $25 one-way, but could fit 4 people into a car and more into a van (not sure on the cost of the van)
3) Towncar - not sure on the exact cost for a trip with this
4) Rent cars for the day (a 15 passenger van runs about $150 plus gas for a one-day rental). Otherwise, you may need at least 2 cars or minivans
Looks like this will cost about $150 in transportation, whichever way you choose