Hi i've looked into getting 2 pontoon boats as there will be about 20 of us afaik. I found this info:
MAGIC KINGDOM WISHES CRUISE (PREMIUM)
25' Tracker Pontoon
Price: $346.13, tax included for up to 10 guests. Price includes pontoon boat, driver, water, soda, bagged snacks and audio feed of the fireworks music -Guests may order Private Dining to be delivered to the cruise. The sound from the fireworks show is provided on the boat
X 2 = $692. I dont know how long this cruise lasts for though but i think i seen something somewhere saying it leaves half an hour before the fireworks are due to start.
Also have some info on the Grand I as I had looked at this too but its not big enough for 20 ppl.
VIP CRUISE ON GRAND I YACHT a 45-foot Sea Ray yacht staffed by a captain and deckhand, 17/18 guest maximum, available at Disneys Grand Floridian Resort & Spa.
Price: $480 for 60 minutes $720 for 90 minutes $960 for 120 minutes Call (407)-824-2682 to book.
Hope this helps, Eve