If the table and chairs are old and well used there will probably be a build up of old wax in some places, together with some grease (from hands and fingers over time), and it could be this which has resulted in the variations in colour. So, I would suggest a general clean-up and look-see before you re-wax.
I wouldn't use an abrasive paper as you would no doubt find that the residues on the surfaces would clog the paper immediately and you would end up spending more on abrasives than the table & chairs cost in the first place.
I would suggest that you use some kind of solvent with an abrasive pad - a green nylon kitchen sink type scourer would be fine - keep turning it as you progress and don't use too much pressure. This should remove any residues without damaging the surface. I would avoid using wire wool as there may be little nicks or bare patches where you find you are abrading bare wood - and wire wool and oak don't go together! The wire wool reacts with the tannins in the oak to leave black stains which you cannot remove. For a solvent you could use one of the Colron range of cleaners, available in most DIY sheds, or ordinary white spirit.
Then a good wipe down and on with the waxing - best of luck.
If all of this is no good (you might want to try just a bit first - say one chair back) and you decide on a full strip, re-colouring and refinishing, set aside loads and loads of time before you start!!