We did this in October and were on the wrong side of the boat. We had a great view of the water pageant, but the fireworks were just average I would say. My 6 yr old actually had a bit of a paddy because she couldn't see well. It depends a lot on the other people, we had some families who stood their kids on their laps on the fireworks side, which was quite a barrier. You can see everything yes, but its not an unobstructed view and there will be heads in the way. You're viewing a narrow strip of sky between the boat side and the roof / canopy. I was a little annoyed as we booked as soon as the booking opened - like I was ringing every morning for about 10 days and being told its not open yet, so it wasn't like they gave priority the earlier you booked.
It was lots of fun, and I don't regret doing it, but its better to have realistic expectations. Also if you're last off the boat at the end, and you want to meet any special guests, be prepared to wait. As you can imagine, 100 people in a queue, if you're at the back that's an hour of waiting.
Hope you have better luck!
Sencybil
xx