You have set up a big challenge and change for yourselves...all very worthy and all needing to be done. Don't lose patience with yourselves as you make the changes. Figure this will take about an entire year to accomplish.
My suggestion is to document a baseline for yourselves. How much did you smoke? What is your height, weight, and stamina. (Can you walk up one flight of stairs without huffing and puffing?) What times did you eat? How much coffee did you drink (2 cups in morning. 2 at lunch 2 in the afternoon, 2 at dinner, etc.)
Once you have established your baseline, then any achievements can be measured against that. And you will need to see those achievements. Even if your coffee consumption goes from 2 cups in the afternoon to 1, that is an achievement. Make sure you check your baseline at least once a month and document the improvements/changes.
Then work on substitutions. If you are not smoking, what are you substituting for it? (not candy! please!) The action of smoking (the habitual reaching into your pocke) will need to be replaced with reaching for something else and then finally not reaching at all. Put something in your pocket that you can reach for...be it a pencil, a toy of some sort, anything that you can substitute for the cigarette.
A child will cry and cry if you take away a toy or some food or anything at all...but if you subsitute it with something else, the child is content. So take away the bad food and the bad toy and substitute it with something good.
And yes, join a gym, but even more important, join a support group of some sort. Surround yourself with people who are living a healthy, active lifestyle, and soon you will be too!
And next year, when you take out your baseline and compare it, you will be astounded at the improvements, all baby steps...one at a time.
Good luck!