I'm using ooVoo to do face-to-face chat with my friend in Brazil. I'm in California.
WhatsApp allows you to send up to 2 minute voice recordings.
As for your friends- if you suggested Skype in the first place, and it's worked so well for so long, wouldn't a more modern, updated app make sense to the user after the track record of the app you suggested before, and a quick explanation as to why?