Travelling from UK to Greece with toddler?

Mummy Moo asked: Are there any vaccinations she needs to go on holiday from UK to Greece? Any tips to make the plane journey easier on her? (Hoping breastfeeding will help!). Any other advice would be much appreciated!

How can I stay in Greece longer than 90days? I’m a new zealander living in UK on working holiday visa?

Rachel asked: and what would happen if i stayed in greece 3 months and then went to anohter schengen country? what would happen if I overstayed? Thanks