If you have the email addresses in your data source, it is pretty simple you just need the syntax correct.
When creating the data connection, on the email properties, use the formula buton on the right of the To: line and enter a formula to concatenate the email address string.
concat(email1, "; ", email2, "; ", email3)
The entry needs to be formated just like Outlook or any mail would, each address seperated with a semi-colon, I believe the space is optional.
This would create an email that would be sent to the three dynamically. Obviously the formula could have filtering, etc to ge tthe emails of the users selected.
Hope this helps.