I was totally terrified the first time I went to give DD toast, actually, it was around the same age as your DS. I don't know where I got such fear of choking from as it rarely happens. Of course, once I actually gave it to DD (watching her like a hawk) I realised my fear was a bit over the top. I think if your bub is interested, then give him a bit and see what he does. One thing I kept in mind is that its good for them to clear their own throat, so if your DS caughs a bit - don't panic. Offer him a drink to wash it down, then let him at the toast again. Its also really quick and easy to scoop a bit out of their mouth should they bite a bit off and you don't feel too comforatable about it. One other thing I did was a Baby First Aid Course - highly recommended. It taught me lots of things, including how to deal with a choking baby. I think that gave me a lot more confidence as I knew I could handle some-thing, should it happen.
Best of luck - I bet your DS suprises you with just how clever at eating he is !!!
DD is 3yr 8 months - DS is 6 months