Using many phone numbers on iPhone

facetime and imessage don't require a sim card they work over wifi too

sim cards each have their own number transfering the number when you change carrier takes weeks in most places

simc locked phones can never use other sim cards then one from the carrier they are sim locked with

only the carrier can unlock the phone

you can use your vodophone sim card in the rest of europe well likely the rest of the world this is called roaming

http://en.wikipedia.org/wiki/Roaming

the eu is working on removing the extra cost of roaming in other eu countries

Any contacts and other information will remain on the iPad and iPhone. I suspect your phone number will change each time.

If you set up messages and face time to send and receive with your email address/ Apple ID rather than a phone number, it will allow your family to reach you no matter what phone number your SIM card determines you use.

As long as your family has your email address and phone number, they will get a message updating your phone number for iMessage and FaceTime with each SIM card change.

You don't need to remove the phone number from the iPad, but you can check the email and uncheck phone number by going to

Settings

Messages/FaceTime

Send and receive

Happy to help, have a safe journey.