I advise people to exercise for the health benefits rather than to burn calories. Stronger heart and lungs. Better breathing rate. Relieve stress. Improve metabolic rate. Burning calories is the side-benefit that accompanies all that
The reason I advise people to exercise for the health benefits rather than to burn calories is because you aim to find something you will enjoy rather than something you see as a necessary evil. You will not keep something up if you do not like it
As for how much you should be doing... as much as you can squeeze in at a pace and frequency that suits your fitness level and schedule. You say "we", so I infer you are roping in your partner (or the other way around

)... but our bodies are different. If you have more muscle mass then you will burn more calories for example
Now running v walking. People will tell you running will burn more calories. Not strictly true... If you walk for 50 minutes or run for 20 minutes you will burn the same amount of calories. So high intensity, bigger calorie deficit