I'd keep it simple for now. Treadmill 3x a week for 30 minutes.
Go for a normal setting, no inclines or fluctuations, then after 3-4 weeks of getting used to it, switch to an interval setting that won't become adaptive and will retain efficacy.
That should be, coupled with a better diet, a big step on your new road.
Be proud of making this decision and for trying to see it through. Your children need a positive rolemodel, so this is where you really start to show them, exactly what such a person is.
Good luck

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