When you say "don't want to have it when I'm there" do you mean unprotected sex or your period?
The combined pill is taken for 3 weeks with a 1 week break (usually) and you start your "period" in the break week. You remain protected throughout the cycle and can take 2 packs back to back to delay your period.
The mini pill is taken every day with no breaks. It can make your periods lighter or even non-existent, but it is quite unpredictable at first. Some people report fewer side effects, but some people like a "period" to know everything is working as it should.
(the bleeding in the week off is technically a withdrawal bleed caused by the removal of the hormones and not a true period).
If you are wanting to delay your period for the festival there is a drug specifically for that called Norethisterone and available from your doctor or chemist.
Do note that if you start on the pill (at any point other than the 1st day of your period) you are not protected from pregnancy for 7 days. Also if you are going to be sitting on dirty willies at a festival, make sure you use condoms as well - belt and braces.