Laptop Choice?

Sharing is easy, each person logs in with their google account. There are various parental filters built-in.

Full Powerpoint isn't an option with Chrome. Your choices are either run the Android app or use Powerpoint online (I don't use powerpoint enough to know what those options lack but you can test in any browser/android phone).

Sheets will run fine as obviously it's google based and all in the cloud. Rstudio has two options, either the cloud option or some of the newer, more powerful, chromebooks can natively run Linux apps so you can install and run it that way (actually you can also install Linux via Crouton and run it that way but it's a bit of a hassle).

Telly can be done via websites or Android apps (although not all play nicely).

I don't know about specific models but certainly get one that can run Android apps, 4GB of RAM and think about a minimum of 64GB of storage if you're planning to install a lot of apps or do stuff locally rather than on the cloud).

Generally it's a matter of deciding on form factor and budget and seeing what's available. Obviously you'll pay more for a slim, lightweight model than something a bit bulky and plasticky.