The PS and AC belt are actually removed to access the timing belt. So replacing them with new parts is very prudent as they are wear items and labor is inclusive with timing belt change if you decide to change or not.
The water pump is exposed typically during a timing belt change so very minimal labor is involved in replacing it.
Do the AC & PS belt for sure as it is a parts only charge. The water pump is a prudent measure but not required. If it fails it will at least cost you around what you were just quoted to replace the timing belt and water pump. Also failure of a water pump can lead to catostrophic engine damage if you continue to drive the vehicle in an overheated state.