Hi Francesca,
You are definitely planning on a very special trip thinking about those
private/specialty cruises, they are something spectacular! You have various different options, but let's start at the very top of the class, if you are really looking for a magical experience, then do look into renting the Grand 1 which is an indulgent 52-foot Sea Ray Sedan Bridge Yacht available for luxurious cruises accommodating up to 18 people (17 if a Butler is in service) around the Seven Seas Lagoon and Bay Lake. This is the perfect place from which to watch the fireworks from Magic Kingdom. For reservations or enquiries call (407) 824-2682.
Next, you have your Celebration Cruises for up to 10 people, depending on the boat size, that are perfect for celebrating a very special occasion. You can call 407-WDW-PLAY or (407-939-7529) to make reservations for this type of cruise or to get further information.
Let's go onto the not-so-private cruise options and my favorite one here if you don't mind having fun with other guests joining in on the same cruise experience with a Pirate Theme is
The Pirates and Pals Fireworks Voyage. This experience is just plain fun and laughs while at the same time breathtaking as you watch the fireworks at Magic Kingdom from the water. Please see the link above for a detailed look at what to expect from this special event. To make reservations,call (407) WDW-PLAY or (407) 939-7529 up to 180 days prior to your visit. I hope I have helped in giving you a few different ideas depending on the level of "privacy" you are looking for (and maybe budget as well). Whatever you decide, have a magical adventure!
Best wishes,
Brigitta