For these kinds of situations, power banks are great. I get the impression that they're not very popular in North America (dunno, haven't lived there for a while), but they are everywhere in Asia. I just bought a new one that gives me over 10k mAh. Enough to charge quite a bit of both my phone and iPad (and it comes with both USB and Lightning connectors to boot). For a long weekend or vacation, it's well worth packing these things, it's not like they're cumbersome or heavy either. About the same size and thickness as my phone for 10k more mAh.