Hi T.-
My older sister and younger sister are 8 years apart. For great times together, these are some of the things our parents did with us.
1. Plant a garden- grow your own squash, corn, pop corn (that one is really fun), lettuce, carrots, tomatoes, etc. Make it a project that they love and can see the results from. Also plant fruit like strawberries, blackberry or boysenberry vines, etc. We used to love going out in the morning and picking fresh berries for our breakfast. It was amazing (and I am NOT a morning person by any means!)
You can also do a couple of trees, like a lemon or a plum. THe other thing for gardening is an herb wheel. A two tiered herb garden with things like mint, opal basil, st. john's wort, etc. These are gorgeous when filled out!
2. Set up a water day- swimming, races, etc. Then after everyone is tuckered from swimming and such, go home for pizza and movies.
3. As far as baking goes, maybe get the ingredients for a sourdough starter. Make your own- you can add things like apples to it to feed it, etc., when it gets stable, and then get up daily with them and bake a loaf or two- or on the weekends, bake break for the week, make loaves for the local homeless shelter, etc. But with the things your girls love to do with you, you can feed your family and lower costs for groceries, etc.
4. Plant a garden- do some foliage, some flowers, and get some things together that will beautify your home and also give the girls something to work on and watch daily. Starting from see is great- I have some grape seeds that I saved and am trying those. Get an old egg carton (cardboard) and start the seeds. When the seedlings are hardy, transplant them.
5. A kitchen garden. My Secret Sister at work gave me a book called the kitchen garden cookbook. It has tips for growing herbs in the kitchen, on the counter, and cooking and baking with them. That may also be a neat project for both of your girls.
I hope this helps and inspires!
Good luck!
-E.