The body needs carbs to regain weight (insulin is a building hormone). White sugar actually gets adrenaline going, which is counter productive since adrenaline is a weight loss hormone. (Ever see a skinny sugar junkie? I have!)
So, concentrate on complex carbs, healthy fats, proteins, and vitamins so the body has everything it needs to start building again. Exercise should be moderate cardio (30 minutes, 3 times a week) OR walking 3-5 miles per day. AND weight lifting 2-3 times a week.
I have no way of knowing how many carbs y'all should aim for, as it just depends on your own metabolisms. A good general starting point is 150g/day. If that seems high.. well it has to be to get you gaining. If it seems low, then add 50g a day to what you are currently consuming.
Increase the carbs by 50g/day each week until you stop losing weight.