From the MSLT for Office 2010
12. HOME AND STUDENT SOFTWARE. For software marked “Home and Student” edition, you may install one copy of the software on up to three licensed devices in your household for use by people for whom that is their primary residence. The software may not be used for commercial, non- profit, or revenue-generating activities.
You may also wish to find out whether your and your wife's employer participates in the Home Use Program, as that might be an alternative cheap and legal way of getting hold of a couple of copies of office for home.
See here.