How do I calculate the Sample Size for this type of Survey?

Hi all,

I need to calculate the sample size for a survey I will be undertaking soon. The target population will be the clients of 8 hotels, forming part of the same company. The objective of the survey is to get the profile of the clients and their level of satisfaction.

I've read that if the target population is known and is specific, the population size does not matter much for the determination of the sample size. If that is the case, how do I go around for choosing my sample size?

Since the clients are of different nationalities (French, British, German, etc...), I want to ensure that each nationality is fairly represented in the sample.

Any ideas on how to proceed?