Brother I believe you need to fine tune your plan.
First of all if you take NATCO, it will take around 20 hours minimum to drop you at gilgit. So you have to have a peaceful sleep and rest to be recharged for the next day. Therefore, include 2 days from RWP to Gilgit.
Secondly, for Naltar you have to take left from Nomal and the track from Nomal is around 3.5 hours by car / hi-ace and around 2 hours by 4x4 to Zero Point. After Zero point you have to book 4x4 to visit Pari Lake and Satrangi Lake, which I believe will be 1 hour drive and very uncomfortable. While return, you will have to stay and enjoy the Naltar forest and see the Snow Leopard. This is one part. Second part is to go to ski slope and enjoy the ride on chair lift. which is around 30 mins from Zero Point. So I believe, you should have to stay at hotel there in any case as travel back to hunza / gilgit after day time is not suggested at all.
Then on the next day you can easily go to attabad lake and visit passu cones and glacier and also go to khunjerab to and on return stay at sost.
Going to skardu from gilgit / hunza for only visiting shangrila and sadpara is illogical. Rather you should visit some other areas like phander or Nagar and hoper.
Rest is your call.
