While I'm not familiar with the LG devises, I will say that your iPhone4 is obsolete and no longer supported by Apple and may (may...) not be allowed on a cellular network. That being said, it doesn't sound like you're interested in getting a pay-as-you-go SIM card for it anyway.
In order to avoid racking up roaming fees, place the devises in airplane mode as soon as you board your flight and leave them that way for the duration of the trip. You can then turn the WIFI on and off (but leave the phone in airplane mode) in order to connect to free WIFI.
As for battery charging, take the appropriate battery chargers and power adapters. Modern electronic are dual voltage so the 220v found abroad is just fine and you DON'T need a voltage converter. You might also want to look into a small emergency battery devise. Something the size of a lipstick case can hold enough juice to recharge a phone.
A word of caution - do NOT go to any web site where you must enter credentials (username/password) in order to access the content while on a free and unrestricted WIFI network. This goes for everything from email to banking/credit card sites. If you to use your devise for banking or email use while traveling, install and use a Virtual Private Network.
As for being a tech novice, check your local community center or community college for non-credit technology courses geared for novice/casual users of technology.