Getting technology ready

I am going to the four day Cambridge Folk Festival later on this week, living in a tent in a field in the (forecasted) rain.
Its been quite a few years since I managed to get festival tickets and the first time sort of on my own. D2 will also be there but staying in the campervan park that is some way away. I therefore need to be contactable and my phone is very good for about 10 hours and then it dies. I have borrowed these power packs that should see me through but they need to be full charged to start with to be any good.
The other piece of equipment being charged up is a battery powered air pump for my air bed. I am too old to sleep on or close to the ground now a days.
I am gradually collecting all the other gear I will need to take. I seem to be missing a battery powered coffee machine. Without one of these a ready supply will have to be found quickly on Thursday to enable me to keep going all weekend. People using drugs are a problem at festivals but caffeine does not count