We just booked ours for our trip in May to see Wishes.

CM Brighton answered all my questions and more than I could of ever thought of.
They are called "Specialty Cruises", and the Illuminations one only has 3 pontoon boats and the Breathless Yacht, all departing from the Beach Club or Boardwalk. The Wishes one has as many as 20 boats they can call on, and depart from CR, GF, WL or Poly. The cost for renting one of the pontoon boats is $140.84 plus tax, which includes the boat rental for 1 hour and the driver/captain. They hold up to 12 people (only from your party--you do not share), and do supply life jackets (if wanted/needed--I think it's required for the kiddos). The Breathless Yacht is only for Illuminations, and accomodates 7 people for $179.24 plus tax. There is no food or drink allowed on the Breathless, but you can order it for the pontoon boats. They have three tiers of food service:
Tier 1: $187.79 plus tax
includes:
-boat rental and driver/captain
-sandwiches, soda/water and a snack
-for each add'l person over 4, cost is $18.78/pp.
Tier 2: $258.51 plus tax
includes:
-all of Tier 1 plus dessert, fruit and cheese
-for each add'l person over 4, cost is $46.94/pp.
Tier 3: $328.63 plus tax
includes:
-all of Tiers 1 & 2 plus alcohol (ie. champagne)
-for each add'l person over 4, cost is $46.94/pp.
Also available is food a la carte, such as champagne ($46.94), chocolate covered strawberries ($11.94), etc. Ask the CM when you call what's available.
There is also a Birthday package, which costs $206.57 and includes the boat rental and driver/captain, 1 round 8" birthday cake (chocolate or vanilla), soda/water, and decorations for the boat including baloons and such...all for up to 12 people.
You reserve with a credit card, but it is not charged until you check-in at the Marina Kiosk, or if you don't show up without cancelling at least 48 hours in advance. They do still sail if there is a little bit of "weather", so be sure to check if you have a reservation and it looks questionable. If they sail and you don't, you'll get charged.
CM Brighton told us she's rarely heard a bad thing about the Illuminations/Fireworks cruises...many people make reservations to do it again another visit. One thing she did add...the Illuminations boats all crowd under one bridge to view the show, so the boats are fairly close together. The Wishes boats have a whole lagoon to spread out on in front of the castle, so they are more secluded from one another.
Good luck!
PS...don't forget to tip your captain and deck mate (tips are not included in the cost)!
