Great pics!! I really enjoy those before and after shots. Now that you can get in there and mover around, it will be easy for you to maintain it and even widen it if you want at a later date.
As for the grass seed, nature sends out seeds all the time, and they can last years until the conditions are right. I'd put rye down when you're ready for it, and it will sprout a few days after your next rain. The stuff to be careful with is hulled bermuday. If you spread un hulled, it will sit and wait until conditions are right, but hulled needs to be planted just before a rain as it will rot and die fairly quickly without the hull on it to protect it.
Eddie