A good idea. You can also:

Move your pension scheme into environmental investments.

Sign up for an energy supplier that undertakes to source all/most of its energy from (near) zero CO2 sources.

And of course reduce personal use: e.g. car use, meat eating, etc etc

The carbon offsets seem suspiciously cheap but this may just be because they are going for low hanging fruit, as more people sign up the price should go up!

Of course the indistry needs regulation and that will probably be complicated.