Hey Kim,
I feel like we deal with this every stinkin' event! What we do is this...on each of our event registration forms, we have a check box for "I would like to bring a guest" ... it's really our contact sales button, but you could conceivably use any checkbox here.
Then I have an alert function set up that whenever the check box is checked on this field, an alert is sent to our events coordinator saying "Bobby Bobberson has ticked the checkbox and would like to bring a guest. Please follow up with him!" so that she knows to give this person a call and get guest details. It's also important to have a change data value trigger/campaign in there to turn the check box off after the event happens as well...
We then track this in an excel spreadsheet outside of Marketo. Like you, we don't want random bits of information about a person that is typically a spouse and often a stay-at-home one or, at the least, usually someone we don't care too much about.
If they are a person-of-interest, we'll find that out at the event and add them to Marketo afterward.
It's annoying to run this in Excel and outside of Marketo...but we don't have iPads, so we can't use the event app anyways 😞 Hope this helps, or at least gives you some ideas!
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