I think you just need to be observant of how your ds manages or doesn't manage the different things he does. If he can cut with your scissors and doesn't get a sore hand then that's good but if he can't cut very well and/or gets a sore hand it might be the scissors rather than his ability. In those circumstances it might be worth trying different scissors before worrying about his co-ordination/eyesight etc.
I didn't know about left handed rulers until after finishing school and would have loved one, especially while doing maths, would have made measuring and drawing certain length lines etc easier.
I have always felt odd when sharpening pencils so a sharpener with the blade on the other side would have been useful.
I have always had left handed or ambidextrous scissors (mum and bro are lefties too). Currently have two bread knives, one right handed but the other is sharp on both sides of the blade so I use that one.
You can get left handed watches where any buttons are on the other side of the watch so they don't dig into the back of your hand when you bend your hand up.
If ds is going for guitar lessons it would be worth borrowing/hiring guitars before buying to see which he finds most natural. Just recently at church a member of the band who is left handed but can play both ways said his next guitar was going to be a right handed one as the left handed ones are noticeably more expensive. If you can avoid buying left handed guitars then it will save money, not just for you now but for your ds when he buys his own as he might resent having to spent extra when he's older if it was possible for him to learn right handed. This might apply to other instruments too. Also, music teachers can be more expensive for a leftie. Drums need set up as a mirror image etc.
I think for sport and music playing/learning it all depends on how left handed you are for what adaptations need to be made. I write with my left but have better hand eye coordination for sports with my right hand, when I worked this out I improved with my rounders/tennis/badminton etc. But still played hockey, netball etc left handed.
A 'see how he does and adapt things when he struggles' attitude is useful. Just be aware that someone not being able to do everyday things might not be because they can't do things, it might be that they would find it easier with a more suitable tool, doesn't just work for handedness, useful for different disabilities and just in general.