Howdee..... Fresh wood should be allowed to dry 4 to 6 months. Will old sticks and stems add flavor? Yes but IMHO its not the same intensity as center chips, chunks, or splits. Is it better than no smoke? You dang skippy. A suggestion, get a can like a used spam can. with a can opener, opens some holes around the botton and use this for you sticks and twigs fire box in your pit. Set it in the opposite end from your coals That way it doesn't cook off too fast.
I have pecans in my back yard too and I love pecan. You are pretty lucky to have such a swwet smoke just laying on the ground.
Now might I recommend that you buzz over to the "Roll Call" forum and introduce yourself so you can get the big boy hello's from all the Guru's and they will help you get aqquainted with the sight and how to easily manage your way thru. Seriously the introduction doesn't hurt, bad.
If I can be of any other help, just let me know. Again, its a pleasure meeting you.
Enjoy the smoke.