My personal opinion:
If your going to be over there again and again to re-do or "freshen" up the coatings once a year or once every two years.
Why not get epifanes or a good clear sealer (non** oil based)?
I've never run into an oil base sealer than doesn't change the wood tone to either a brown / yellow tint. I know with "clear" *water* based sealers it won't change the tone and if it does it won't be several shades noticeable.
I personally would go with a good sealer, spray several coats with a scuff sand between coats for adhesion (3 coats total). Just make sure if you do, you get all the way around the gate (sides, including bottom). Plus with the summer heat, the water based sealer will dry pretty quick so you can probably get 2 coats in, in 1 day.
Just a personal opinion. Good luck and let us know what you ended up doing!