Some things kids like to do is learn something interesting.
Like making bread the old fashioned way.It takes all day and they can watch it rise and bake.
You could buy some wheat berries,fill a tray with indoor plant mix,sprinkle berries on top ,gently press them down and keep them watered with a fine spray.
Be sure the tray has holes for drainage.You can buy them for that purpose.
Set them under cupboard lights or other florecent lights,about a foot from the light.
It's interesting to watch the wheat grass grow and it's good in salads and super nutricious.
You could use them for researchers for anything you need to know during the summer ,maybe for some winter project you might be doing next winter.
Just give them any job on the computer and they're happy.
Maybe research and download some of your music.
Many magazines advertize for pen pals for same age students in other countries.
For middle age kids you could start a penny ante club where no one loses much but they have that competition going.
For younger children you could make a weekly trip to the library and reward reading with a movie and pop corn,or something else they consider a reward worth reading for.
Take them to dollar stores and garage sales to buy stuff for the Secret Santa Box early.They will be happy to be boss of the box.