the proper "parade" (do we still call it a parade?) is only going to take place between Chelsea/Battersea and Tower Bridge, so that's where you really need to be, but the boats will begin to form up as far back as Hammersmith, and then begin to disperse after the Queen has reviewed them at Tower Bridge.
So you should still be able to enjoy a huge number of them at Greenwich. Although which ones, and what time they will get there, is all up in the air. The official order of events
that we have seen only go as far as Tower Bridge. And we haven't seen any information about the Royals going further than Tower Bridge either.