My advice... TAKE THE OFFER. Take it and run.
Based on your description, it's exactly what an internship needs to be - a solid experience and resume enhancer. Take it. Take it. Take it. Enjoy the second half of the year without all that pressure.
And remember, nobody lands in their "dream job" as an intern or fresh off graduation. And if they do, they invariably find out it's really not their dream job after all.
In short, take it.