Stay at PTDC @ Nathiagali and i remember around the same area there were few other decent hotels also so you can check them out too. But i would still stick with PTDC.
For Murree, If P.C is affordable then nothing like that otherwise hmm how about one of the army places?! I dont really think murree has any other nice hotels anymore. Few yrs back they had 1-2 nice places but last i went abt a yr bk everything lukd weird. I remember we stayed at heaven view and tehmina’s lounges quite a few times n they were quite nice bk then but i m not sure about now.
Just be careful with the food and even the accomodation because nowadays as it is people r getting sick with diarrohea and what not so just be extra careful with everything. Have a great trip 