Help Ben to walk properly

Ben was adopted from the RSPCA as a pup at 8 weeks old. He is a gentle giant and a very much loved member of our family.  We choose to adopt a pup from the RSPCA to give a dog a loving home and a chance to live a happy and healthy life. For Ben this has not been the case.  As he has grown now 15 months old, he has shown signs of discomfort in the rear end and was walking on his toes.  I had him x-rayed and the results were not positive. Ben has hip dysplasia on both sides and a floating patela on his right knee coursing him to not be able to walk far without a great deal of pain. After medicating for pain and making Ben a little more comfortable the vet has recommended a full hip replacement and knee operation that will cost over 12K for the both operations. Some would read this message and would be thinking the most humain thing to do is to have Ben put to sleep.  We did consider it but as he is so young he has so many years ahead of him if we can give him a chance to walk without pain we will. 
As a single mum with 2 kids the money is no were to be found. I have exhausted all options to assist with raising the funds with no success. My heartaches at the thought of not being able to help.  He bring so much joy to my family, laughter and challenges. So we are here asking for any donation you may be able to spare.
As soon as we can raise the money for Ben he will have his operation and will be able to live his life to the fullest. 
Thank you.