Kids are so used to being entertained, the lose their creative side! For fun, go to the library and get a book of old party games. I used this for years at my son's parties and everyone thought it was so cool that I "invented" fun games! Potato races, for example. Or "the memory game" where you put a bunch of objects on a tray and cover them, then remove the cover and give the kids 1 minute to study, then cover or remove the tray. Then they list all the things they can remember. Takes a while. This presumes that the 5 year old can write well enough.
If you have a basement or play area, let them build something that takes time and requires a lot of different things - my kid used Brio train tracks and Legos and K'nex, and mixed them together to build huge "cities". Go to yard sales and pick up toys for a bargain, and let them combine them.
How about creating some sort of habitat out of things they find in nature? Turning it into a diorama or an art project? My son build ant farms with large clear containers (recycle the things that fresh produce comes in). Is there a spot outside they can dig in and create a "moonscape"?
Can you set up an umbrella outside? Do you live on a street where they can have a lemonade stand? Make signs, make change, etc.? If the bugs are mosquitos, if you can put them on a porch or patio with a fan, the "breeze" will keep the mosquitos away.
Can they create a skit or play for the adults to enjoy? By the time they create it, memorize lines and find costumes to wear, it should be at least an hour.
Let them know that only boring people are ever bored!