Dont worry about him. He will play with things in his own good time. For the time being he is sitting back, relaxing and quietly watching the world around him. One day he'll freak you out by grabbing hold of your mobile phone or something... then you know to get him his own toy one!
My LO discovered his hands first. Spent ages looking at them and then moving them around. Soon after he was using his new found hands on the odd toy here and there.
Make sure any toy you try him on has small parts he can grab with his little hands. He still doesnt like anything big and clumpy as he cant fiddle with it (he's 18 weeks).
We are now at the stage where he has discovered his left foot. Cant stop grabbing it... he hasnt figured out he has a right one too!
Stop worrying about your little boy. He sounds lovely and sounds like you are doing all thr right things.
Lu xx