Anteater - may I ?
Yes, in high traffic areas, your varnish will always get rubbed off and then surface damage to the board underneath will occur. An oil finish would be better, and easier to touch up when needed.
(You will need to sand existing varnish off though, the oil won't take otherwise as the varnish makes a barrier).
(Feel free to correct, anyone, if I make a mistake).
Puff, if you get a wet rag / white spirit, and dab at a sanded area of board you will get approximately the colour after treatement with Danish oil. Old pine teeds to look rich mellow caramel brown to strawberry blonde. New pine will tend to look a slightly dirty blonde.
I think each coat will take several hours to soak in and dry, but you can continue to add oil as the surface starts to absorb the oil. You can then wipe away excess, and it is not sticky in quite the same way as varnish. If possible, I would allow to dry overnight before reapplying more, but it probably won't be needed. You can rub down LIGHTLY between dry coats with abrasive synthetic pads / wire wool to remove any minisucle nibs / highs of dried oil.
Not sure how often a "high traffic" area like a kitchen would need before re-application. Anyone ? My guess is that as oiled wood wears in a different way to varnished wood, you won't need to reapply for years. When it looks dull / badly scuffed, plonk some more down. The product does not require immaculate cleanliness like varnish does. It's much easier to work with.
Yes, 2 coats would be sufficient, but the more you can flood the wood intially, the more water resistant and scuff resistant (visually) the floor will be.
DIY stores often only stock the little 1/2 litre or 1 litre bottles. I'd go for a 5l one from Rustins. Have a google. I've used other brands and been unhappy.