How well do they get along and does the 8 year old listen to the 12 year old?? Do a trial run for a week or two and let them know ahead of time if they do well, do the chores assigned, keep the house clean, give you a weekly book report and do so many pages in a math book , etc. that they will be rewarded in some way ( take a trip to an amusement park or something fun with the money you would have saved sending them to daycare) but if not they will need to go to daycare. Or if it doesn't work out have the twelve year old do some odd jobs around town to keep her busy, mow lawns and clean house for the elderly, babysit, paper route, walking dogs, weeding gardens as well as light duty around your own home-- organize your garage, basement, toys, have her be in charge of your garden... and have the eight year old go to daycare. Reward your daughter with something she really likes every week or two-- a manicure, a day with her friends, time shopping with you, a game or movie -- Hard work never hurt anyone, it keeps them honest and accountable and they will be able to save up for something they really want. Kids are really motivated if they know there will be something fun in it for them every once in awhile. It also wouldn't hurt to have someone you trust to check in with them once in awhile or have someone they can go to if there was an emergency.
Food ideas-- sit down with your daughter and son and let them assist you with a menu for the month. Kids like to be involved and they will more likely stay with the menu if they help with it. Quesadillas are easy in the microwave -- flour tortillas and cheese, meat, black olives or whatever they like , scrambled eggs in the microwave, baked potato (in the micro) with cheese and toppings, sandwiches (tunafish, eggsalad, meat, cheese, pb&j), soup , burritos, have lots of fruit and vegies on hand. Check out a Microwave cooking or kids cooking book from the library. This will be a great learning experience for your children to learn how to make their own food and enjoy it. Just go over some safety guidelines with them and let them know that part of cooking also includes cleaning up. If you trust them and they are responsible they will do well. I hope you and your kids will have a great summer!