I usually take my MacBook Air for work-related needs, but it sounds like an iPad or an iPad mini would work fine for you. Since you are already accustomed to the Apple ecosystem, I would definitely choose some sort of iPad over an Android tablet.
I wonder, though, if you really need to take a tablet for mapping, mail and Facebook. Your iPhone may be all you need. The large screen of an iPad is easy on the eyes, but you will have balance that against the extra weight.
Use your iPhone -- with cellular turned on -- as your daily walk-around computer for mail, maps, and the occasional web/Wikipedia fact check. (Make sure to get an international plan from your provider. Keep cellular on, but turn it off on an app-by-app basis for all but the most essential apps. Also, turn off image downloads in Mail.)
If you have room, take an iPad (Wifi only) for use on the plane and in the hotel. Download some movies and books to keep yourself occupied on the plane. Use it at the hotel in the evening for web surfing.
You could choose either an iPad or an iPad Mini. Really, it's whatever you are comfortable with. My own preference is for a small phone and a large iPad.
As for memory, you don't need much for email and maps. I would get a mid-sized amount of memory (64GB?), unless you are planning to download a lot of movies or a photo backup, in which case I would get as much memory as possible.
My most essential app for traveling is Maps With Me, an off-line map application that uses almost no cellular data. I use Maps With Me all the time. Some other apps that come to mind (in addition to Mail and Facebook):
- Google Translate -- and make sure to download the modules that let you use your camera to translate text.
- various airline apps (very useful for checking flight status and baggage)
- Google Maps -- I rely on Maps with Me most of the time, but once in a while Google Maps can come in handy for finding ATM machines and such.
- public transit apps. The transit systems for most major cities have apps to help you negotiate buses and subways.