In order to view and interact with Mashups, your coworkers will need to authenticate with ThingWorx, which is done using HTTP Basic authentication. As such, you'll create a User for each of your coworkers. Then, you'll apply Permissions for Users to specific Entities. While you could apply individual Permissions for each User, a best practice is to assign Users to a User Group and apply Permissions for the User Group.
To answer your second question, you can provide your coworkers with the same URL that is generated when you select "View Mashup," albeit without the fromBuilder portion.
For further information, consult section six of the wiki, entitled "Security."
After you have given them proper permissions, you can also set their Home Mashup on their user profile and give them a generic link to Server/Thingworx which after login will redirect them to the Mashup assigned.If you want to give them a direct link, it is better to just give them Server/Thingworx/Mashups/NameOfYourMashup, sometimes the composer will launch the link with some extra encoding.Remember that if you have a Master, you have assigned it to that Mashup.
Thank you for both of your responses. I'm currently trying Pai's suggestion, using the Server/Thingworx/Mashups/NameOfYourMashup on an iPad running iOS7 (I assume you can view mashups on an iPad since the preview and builder allows you to view what it would look like on one) and for some reason I can't visit the mashup. It gives me the error "Safari cannot open the page because the server cannot be found". It seems like Safari automatically adds in www. and .com after the server which is probably causing the error. Does anyone know of a fix for this or how I can view my mashups on an iPad?