How is the bonus different from any of the rest of her salary? You sound greedy. My wife sometimes gives me a portion of excessive overtime if she does a whole row of doubles, but it's because I run the house while she's away and she shares of her own accord, not because I asked. If you really MUST have something as a response to the bonus, convince her to spend the bonus on something you need for the house or the wedding.
iPhone app user; excuse typos...thanx.