Oooh, I love planning other people's vacations, vamp127. Do you mind if I give you some thoughts? (5 kids, all older teens and 20's now. Vacations I just drive the younger ones where they want to go and drop them off. Not so much fun.)
Any childrens Museums close by? Call. THey often have specials for vacations. Ours used to offer "science on Sundays" for older kids, and the little ones had a great time with bubbles and climbing structures, and toy kitchens and stores. (I loved it too!)
THe playgroudn is great for the older two, but not so great for the 2yo. COuld you take bubbles for the little ones to chase while the older one ran around? Does the little one like the swing?
How about a kite?
A day at the beach. Not to swim, but to picnic, pplay in the sand, build a sand castle. You get cold so it's fun to bring hot cocoa, or soup, or something. State parks are great for this, you can even have a BBQ.
Clean up Day. Yep, you wanna plan these fun days? THen ya gotta help out. Everyone does an extra chore or two!
The public library. As my 23ds says, "I dont' know why EVERYONE doesn't go to the library! All the books, even the videos are free!"
They also offer programs during vacation weeks. And videos to watch later! You could get one to watch with just your older child, with popcorn after the little ones were in bed.
A picnic anywhere
is fun. You could take lunch to the playground, kids even like eating in the car.
A day in the city is always fun. Go to your local big city (even small cities are fun) to explore, walk, check out history, get lunch (or picnic!), buy roasted peanuts or popcorn from a vendor.
Write down what days you're doing what things, so the kids aren't constantly asking WHEN. It also keeps me from putting it all off till it's too late! LEt them know you have stuff planned. Stuff to do at home? Jigsaw puzzles, playdoh (you could get your older child Fimo), Make-your-own-Pizza night, (in fact, we used to have cereal for dinner on occassion, or oatmeal, and watch tv.) building intricate towers with blocks for the little one to knock over is good for a few minutes.
If you have some money, but the 8 yo the American Boys Handybook, even if it's a girl. The book is FULL of old fashioned stuff kids used to do. SOme of it is dangerous, so use care! (hot air balloons with burning rags to heat the air!) Just reading it is fun, actually doing something from it is great.
Ok, you weren't even asking. Maybe I got carried away. I always LOVED the kids vacations, loved hanging out and doing stuff. Now I need a graandchild!