Im a sahm. Kids 5 and 2. I'm 8.5 stone. I start every day with hot water with a slice of lemon in and walk absolutely everywhere very briskly with the buggy - would recommend these 2 things! Could you park further away from the school and walk some of it?
I also run twice a week but I know that's not for everyone. Even on a non-running day I'm active with the kids. Davina McCall YouTube workouts are also good and she does lots of beginner friendly stuff.
Healthy breakfast ideas - porridge with peanut butter, banana and seeds. Overnight oats with berries. Shredded wheat, marmite on toast. I also have a protein shake but again not for everyone.
Lunch - avocado and chickpeas on toast with veg, beans on toast, jacket potato, soup.
I always have a small afternoon snack - nuts / fruit and alpro yoghurt.
Dinner - I love pasta with chickpeas and pesto, stir fry with tofu, vegan shepherds pie which is made with loads of veg, all sorts of things.
I went vegan 6 months ago and honestly it's been a game changer. I feel so healthy and energetic. If you don't feel able to do that I would strongly recommend cutting out animal products as much as you feel able to, there are so many calories in them.
Good luck.