Current bounce back offer

Is anyone familiar with bounce back offers? I read on chat that beginning last week thru 10/31 a 2016 offer of free dining is available for 5/31-6/7 and 8/26-10/1. I’ve never booked a bounce back offer or free dining, so I’m a little confused. I have a solo trip in September, and would like to book bounce back for my family of four if possible. My main questions are: Can I book a room for 4 if they are not with me on September trip, do I need to check out by 6/7, or just check in by 6/7, and can I add guests to the room at a later date? I would likely book for myself and two kids, but I’m not sure who my other adult would yet…my husband, my mom, or possibly my sister-in-law. Would I be able to add one of them to our reservation at a later date and get free dining for them as well? Thanks in advance for any info you can provide:)