Help regarding an iPad 2

Hi, im a little confused on how these work and what you can do with them….?
My Girlfriend has an iPhone 3GS
(she previously had an iPhone 4 but had to sell it due to bills)
Anyway, I was going to get her an iPhone 4S for Christmas and sell the 3GS to make some of the money back, but 2 people I went to buy 1 from messed me around…
Anyway, a friend of mine had an iPad 2 today and she liked it and said she would love one, so I figured I could get her an iPad 2 instead, then the Micro Sim she got can go in it (which she pays monthly for and mainly uses it to be ‘Online’ and to make the odd calls now and then)
Obviously you cant ring people using the iPad 2?
or send text messages like on iPhones?
So what can you do?
is the Micro Sim clearly just to be able to be ‘on the Internet’ while your out instead of using Wifi?
If she has an iPad 2, is there any point in her having an iPhone 3GS or even an iPhone 4 or 4S?
Are iPads basically just giant iPod Touches which you can use anywhere? (not just somewhere that has Wifi)
Thanks.
Answer #1
I have an ipad 2 and i use a Pay as you go micro sim in it, so i top it up with £20 pounds of data every so often but i find myself barely using it so it lasts ages.
Answer #2
She just asked Apple whether she could use her Contract Sim in it which shes using in her 3GS and they said no :-/
so im going to have to get a cheap iPhone 4 for her to use, then she’ll have to get a PAYG Sim for the iPad,
so shes paying Monthly for the Contract Sim she’ll hardly use, and still have to pay to top up the PAYG iPad Sim.
Answer #3
Why don’t you buy her iPad 2 WiFi model?!