Alles über BarbadosCalls on the island over the landlines are free.
If you like to phone to germany a phone card is the best. You can get it in shops and supermarkets. You can use international phone boxes without problems.
For germany you use 01149, dial the number of the city without the 0, then the number of the person you are calling.
Lump sum for 3 min costs about 25,- to 30,- BDS $.
Mobile phone: You can use your own mobile phone, depending which network you use. (Roaming)
Another possibility is to get a SIM card from Cable & Wireless in Bridgetown and use it in your own mobile Phone, you get your own number for the holidays and you can choose your credit, for example 20, 50, 75 or 100 BDS. Just use a freephone number to activate. You can ask about your account anytime. Often they have attractive offers, like you get a free phone if you buy a 100 BDS card. You can also borrow mobile phones.
Meanwhile it is no problem to send an SMS from Germany to Barbados and the other way round.
Also Internet is not a problem, the easiest is to get an internet card from a shop and just dial in, you can choose how many hours you would like to be online during your holidays.