Love / Visiting Polish Girlfriend at her family. How to greet her family members? [7]

I have been with my polish Girlfriend for 3 months now but she went to Poland for christmas for 4 weeks and we agreed I would come for a week in january.. aka this saturday I fly...

I will be staying with her Family, Mum dad, 2 sisters and 3 brothers...

Can someone please help me with the greeting of family members.. When greeting mother am I supposed to shake hands and kiss cheek.. also what of her sisters... kiss on cheek aswell!?

I know a handful of polish words.. and her parents dont speak much if any english...

When accepting a meal from her mother what should I say...?? Would it be insulting to thank her in english as I would not be comfortable speaking in polish from what i know..

Any other advice would be much appreciated!