When you cast a spell as a bonus action (either because the spell takes a bonus action to cast by default like misty step, or because you use the Quickened Spell metamagic on it as a sorcerer), you are then prevented from casting 1st-level spells or higher as your action. This of course includes the spells that can be cast from many wands and staves.
But what about the Wand of Wonder? Some of its random effects are indeed spells, like lightning bolt (and are therefore subject to the above casting rule), but some are non-spell effects, like making grass grow or rain fall (and are therefore not subject to the above casting rule).
So, if a character casts as a bonus action then wishes to use the Wand, what happens?
He cannot use it, as it might cast a spell?
He can use it, but if the random roll falls on a spell, said spell is cancelled?
As previous choice, but instead of being cancelled, the spell is delayed until next round?