Screenshots

What format are they being saved in?

jpeg would be the smallest...

How to Save Mac Screenshots as JPG, GIF, PDF, and Other Formats (makeuseof.com)

Then saving a section of the screen or just one window would make it smaller...

Take a screenshot on your Mac - Apple Support

Yes, & you can do it & make your Daughter proud my friend! :)

Open Terminal.app in Applications>Utilities folder, double click on Terminal.app to start it then paste in this line then press enter...

defaults write com.apple.screencapture type jpg;killall SystemUIServer

There are a variety of methods however I always use the Preview - Adjust size. For other methods I would Google so you can find the other methods and then you can decide which method you prefer!

With a Terminal winow open just paste it , it''l go in rightafter the % sign/