time, patience, and consistency. with 3 kids if exercise isnt an option (and im sure you get a workouttaking care of the children). drinking alot of water, reudcing overal calories, cutting back on sugar (refined). losing 70 lbs isnt going to happen overnight, but with time and patience, anything can happen.
Whether or not 125 is realistic depends on your overall frame and such. A lot of people kind of set arbitrary weight goals for themselves. In coming down from 265, I take it 5 lbs at a time. When I lose 5 and reach, say, 210, then 205 becomes my next goal. I'm working down to 200. When I hit that, I'll reevaluate and see if more loss is necessary.