there I was knowing I had to brainstorm a lot of challenges to be set in an annual contest. To pick out seven, I thought. But lots would be good to make the best choices.
And then I drop the bombshell on them that they will have to compete -- they thought they were exempt.
Whereupon one (perhaps in revenge) wanders into the library to research past challenges, on the grounds that at the very least, it gives them a good set of problems to exercise themselves on. Meaning that I need lots and lots and lots of them to pick out lots, both for the current ones and the history. They don't like to repeat, though, as one character will sagely point out, that may mean they will repeat when no one expects them to.
Fortunately another character promptly points out that the tasks will be weighted toward the sort of things you would do in royal service -- the contest was decreed by law to inspire wizardry students to aspire to learn -- which doesn't limit it much but does give me ideas.