Now that Aaron is holding his head up, sitting up with assistance, and pushing up to stand I decided to try him in the excersaucer.
The first few times that I tried it out with Peter were a bust (he cried before he was even in the thing), so I didn't get my hopes up too much. Aaron, however, was perfectly content.
He isn't really reaching for the toys yet, but he will sit in it for 15-20 minutes and look around.
I am pretty excited for another way to entertain him since he is awake for a lot longer in between naps these days.