Is my Car safe to drive?

[JB2009]

Ok so I had bought a 2001 Dodge durango 4.7L V8. has 120,000 miles ok it. I first noticed I only overheats when Idling. Well I changed the thermostat and put antifreeze init. Still overheats while idling. Anyways I would like to find out about what could be wrong with it. Any advise on that would be nice. But there is more Today my husband and I drove to the city and noticed we heard a knocking noise it speeds up as we step on the gas but slows down when its cruising and when it idles it soft but yet still there. I am concerned. I bought the car almost a year ago and now finding out these problems. Since it is the holidays I cant get my car in at the moment and I have places I have to go. I would like to know if it is anything to worry about for a short time till next week maybe or if i should try and find another ride to my families home for the holidays. And any advice as to what could be wrong is welcome. thank you