You've mentioned kids wanting phones gadgets etc.
Why does a 5 and 7 year old need a phone or the latest gadgets?
I have a 5 and 8, the little one had an Amazon fire which was 60, and the big one has a tablet that came free with my phone contract, and a 20 mobile from a friend who sold it cheap, it just does calls. He goes out to play with friends sometimes and even if I can see him on the field, or if he is at a friends round the corner, I like to ring and say come home instead of dragging the little one out.
You sound like you're putting a lot of pressure on yourself too.
With regards to food, can you set up a tuck shop at home? Let the, earn pennies by doing jobs, and they can buy 'treats' that way there is a limit. And also putting their snack for the day out, an apple, a KitKat, one bag of crisps, and then you just have to do the main meals and they learn to regulate their appetite.
Cooking things like pizza, with homemade dough will take most of the day. And it's fun.
There are surplus food services near me, do you have any?
My local library does some amazing free activities, what are yours like? Also a few schools in the next town over have some free holiday sessions for children on free school meals. Could you see if yours has any?
Also please remember, boredom is good! It doesn't hurt them. They don't need constant entertainment and gratification.