Help your mother make biscuits for breakfast then use the leftover dough to make all sorts of creations (like elephants or cars).
After breakfast is cleared away bring out the dominoes. You can use them for counting or stacking or building really cool rubber ball racetracks.
If the force of the speeding ball is too much for your wall you may have to improvise a new design.
Your small ball wall may fall if it encounters a big ball. Don’t be too surprised by this. (And don’t let on that you are learning about force and momentum and design and angles and all sorts of other school-y things. If anyone asks, just say you’re playing.)
Practice your piano a little each day and soon you will be able to play any song your sister composes. (using her trusty crayon, of course)
Since some people believe keeping track of time to be an essential skill, consider learning how to read a clock. If that gets boring you may just want to draw a few clocks for fun.