Well done for losing 3 st.
When shopping plan meals ie
Monday, roast chicken,3 vegetables small amount of potatoes.
Cook it and go small with the potatoes or pasta, up the amount and variety of vegetables. Offer greek yoghurt with honey or fruit then NO MORE.
My son has an unlimited appetite, and could easily pile on weight, but after a meal, like above, l just offer a piece of fruit like a banana then say no more. He knows l do not ever change my mind! and he is not overweight....you have to accept you are in charge and responsible for their diets.
Accordingly l only buy what is on my food plan, l allow a very small dessert ( ie tubs of small brownie bites, 2 only) and offer a piece of fruit or plain rice cakes after.
I do however double up on my sons vegetables compared to DD and same if he is having grilled fish, she gets one piece he gets two,( they don't get battered fish except for grandparent treats once a month to the local chip shop)
DH loves crisps so they are kept in a high cupboard and Dc know they are his, also ds9 and dd10 are not allowed to help themselves to food except fruit and nuts, without asking.
Don't let them see you snacking except on fruit, you have to set the example. My late night chocolate bar is private!
Don't be afraid to say 'Here is dinner, we are all going to sit down together and enjoy' Make mealtimes fun then resist firmly all attempts at snacks unless on healthy foods.
On a weekend l often cut up carrot sticks, sweet peppers and cucumber or grapes, and leave out with nuts for' energy boosts'. my dcs now think they are treats!
I find it is so much easier to have only healthy food and very limited desserts in the house, and let them have other treats at parties and on special occasions. Then it is easier to control.
You cannot out excercise a poor diet.
Don't have squash in the house it rots teeth and is full of sugar and sugar substitutes, water or milk is much better.
Good luck with the continued weight loss.