I think it sounds good!!! Will it work out "good" - only time will tell, so keep up with what's happening... but also relax and let it unfold a bit too. If the challenging packets don't seem to be challenging enough, add some challenge yourself for your ds. If he's bringing home books that seem too easy, keep him supplied with challenging books from your public library and send them to school with him for silent reading time.
Also keep up the good communication you've started with his teacher - she seems to genuinely care, so assume she does care
If you want to have a good idea what's happening in the classroom and have time to volunteer, you can also use this as an opportunity to offer to volunteer in a way you can help keep your ds challenged - depending on what you like to do, you could offer to work with the group of advanced students in either math or reading for 1-2 sessions every week during the regular reading/math time. Or you could volunteer just to be a general helper in the classroom during reading or math - I used to do this with reading for my dd and writing for my ds - I didn't work with them directly or exclusively, but by being in the classroom working wherever the teacher needed me I got a great perspective on where all the kids were at compared to my kids.
polarbear