Supporting workflows like this is something we're definitely interested in working on in future versions of the application. The simplest/easiest thing to do at the moment, though, is probably for you both to set up OmniFocus' mail preferences.
Once you do that, you and your wife can send specially-formatted emails to each other; OmniFocus will know how to interpret the mails and use the info to set up new tasks in the inbox for you.
Take a look at the "Processing Mail Messages into Actions" topic under the help menu to get started; if you have any questions, mail the support ninjas
omnifocus@omnigroup.com and you're guaranteed to get a response. (We browse the forums as we're able, but I'm away from the office and will have spotty email access for the next couple of days.)