How to Strengthen the Lower Body and Lower Back?

I'm a 50 year old, heavy set and very stiff. My exercise history is limited to lots of walking the past ten years but nothing else. When i forward bend, i can barely touch my knees. Could you suggest anything that can strengthen the lower body quads included, while saving my lower back? I have invested in a reverse hyper, which has proved quite useful for increasing blood flow to the area. If goblet squats don't bother you, your back, do em just, you know, at you're at your size and your age and the issues.