I suspect they will exist concurrently - so two stays will probably get you two free nights (lucky you!), with regards to timing though - you'd need enough stays in each period, but if your stays are focused in August you'd be fine. I suspect you are better asking MR for a definative answer though as anything said here is pure speculation.

PS: Already discussed this here, as I got it too (Though in my case its a free stays and a free points offer so its clearer they would co-exist.);
http://www.flyertalk.com/forum/marri...-2011-a-6.html