Rooms on the side facing the MK can see the fireworks and the castle in the distance, assuming the room is on one of the upper floors. Not the greatest of views, but it's not terrible either, especially considering it's the cheapest rooms available at WL. When I stayed at WL last year, we had a good enough view from the balcony. Synched up the shows music on my phone and enjoyed it very much. We also watched the fireworks one night down by the water next to Geyser Point (their outdoor bar/food place). The music was pumped in and playing for everyone, the view was partially obstructed, but it was still very nice. I'm not certain, but you may even be able to the the fireworks from the dock.
So to answer your question you definitely can see the fireworks from several locations at WL, however none of the locations are that great.