Originally Posted by
atsak
When I was 16 (which was a very long time ago now, in the early 90's) I travelled from Australia to Canada with two connections via the US on Qantas and US Air (SYD - LAX - PHL - YYZ). Different times in a way; however customs was rude and unhelpful at LAX but eventually everything got sorted out and I did not have any issues following signs etc. I'm sure they'll be fine, but I would simplify their experience with a direct flight if at all possible and make sure they're equipped with cell phones just for emergencies or if customs has questions that have roaming available on them (not all the UK prepaid options do).
Worth pointing out that because the US has an annoying habit of refusing to use the same common standards, frequencies etc. as the rest of the planet there's a non-negligible chance that the boys' UK-bought mobile phones
might not work with any of the US networks even where the UK network has 'international roaming' enabled which could present problems upon their arrival in BOS. Kimovil.com has a handy checker where you can plug in the model of your phone and the country you're visiting and it will show which frequency bands and networks your phone can connect to so check in advance that there won't be problems with 'no network' and no way to call the OP
https://www.kimovil.com/en/frequency-checker
iPhones are fairly universal and useable pretty much anywhere, but Android models sold into different markets (e.g. EMEA) don't necessarily support the 3G/4G frequencies used by AT&T, Verizon et al