Undecided Question

How to care for acne prone skin during Outward Bound?

I will be going for outward bound for 5 days with my school. I live in a hot and humid country. I have acne prone skin. As you all know, outward bound is not going to have any real toilets and we will be spending the whole day under the sun and sweat buckets. Bathing time will also be limited so there will be not time for acne creams etc. Since i will be slathering sunblock(that may clog pores and too strong), my face will be dirting and clogged because of sweat and the lack of hot water(to open pores during cleansing to enable better cleaniness). How do i minimise the chances of worsening my skin and having a breakout? Any tips? Like what should i apply?
Any help is greatly apreciated. Thanks. (:

Oh and my routine there will probably be:
Wash face and apply sunblock in the morning.
Wash face at night and possibly apply acne cream.
That is if i even get to wash my face/use the toilet twice. If we even HAVE a toilet. And provided if i feel secure enough to apply my acne crean in front of strangers.