Sister wants me to set up her son's new tablet 'properly'. What do parents of 9 year olds actually lock down?

My sister's son got a tablet for his school's online homework, and because of my work I've been handed the job of setting it up before their visit next weekend. I can lock it down completely. That's not the hard part. The hard part is I don't have children and I don't know what's reasonable for a 9 year old. Do parents block the browser entirely? Allow YouTube with a time limit? Approve every app? I'd rather not set it up so tight that he finds a way round it in a week, which at that age he probably will. If you have done this for a child around that age, what did you end up allowing?