I was in Thandiani on 4th of August. It is a very beautiful place, you should visit.
Yes the road is narrow and you need to drive carefully, but the plus point is traffic is very less. Just check the weather forecast before you visit and make sure that it is not raining as per weather prediction.
Thandiani is 1 to 1.5 hours drive from Abbottabad city.
Yes i saw some Guest Houses there, but didn't asked for there rates.
I was driving Santro Club 2005 with me, wife and 10 months old daughter.