Take it very easy, at least for few months... I was a little lighter than you about 4 years ago ( I was around 260ihs... and 35year YOUNG). I decided to get back in my good shape ( sub 175 ) and I restarted exercising with good intensity. mainly jogging... I did't realize the toll that almost 10 years of sedentary life will take on you... bottom line I did sprained my right ankle 4 time, my left once and with all the up and down I still managed to get down at less than 210.... than I pop 2 disk in the back.. and welcome back in the 250 after few months of inactivity and physical therapy... now, I recently restarted biking... I'm above 600 miles and feels good. I dropped 20 lbs and it's going down... the bigger benefits are that my BP is dropping, my HR went from a base of above 80 to low 60s... and I also restarted to do some light weight gym. do some simple exercise with a light ( 10/15/20lbs ) kettle bell if you have time... cycling tends to make you lose weight everywhere, including muscles and bones if you start doing for hours at the time.
good luck and have a lot of safe miles.