No need for a converter for any phone or I've heard of. Definitely not for iPhones or iPads. Also would be surprised if computer needed it. I have actually never run into an item that isn't dual voltage. Of course I'm not checking my toaster or anything, just items I'd consider traveling with like phones.
What you want is plug adapters - those tiny things that cost like $2. Get a USB hub that is dual voltage - most are -, put an adapter on it, plug it in to the wall, and you can plug a bunch of USB chargers in at once. Mine has 4. There is probably one with 5. If you need more just bring the plug from home, add an adapter and use as normal.
Something like this
https://www.amazon.com/gp/aw/d/B01L0KNBRC?psc=1
With adapter
https://www.amazon.com/gp/aw/d/B0084OPT8C/ref=mp_s_a_1_11?ie=UTF8&qid=1504779199&sr=8-11&pi=AC_SX236_SY340_QL65&keywords=plug+adapter