If you are referring to Christmas holidays, you should just say "Buone Feste".
"Buone vacanze" also means "happy holidays", but it's especially used for summer holidays.
A standard expression for Christmas greetings is "Buon Natale e Felice Anno Nuovo" (this is usually printed on Christmas postcards).
Just a quick line to add something useful for context...
It's worth noting that it is much more common to say "Happy Holidays" in the US than in the UK although some are adopting it or a form of it there too occasionally. It is seen by some people as more poltically correct as it is then a greeting for ALL with no possible offence of non-Christians...... By others this is just seen as political correctness gone crazy....
You must decide if Buon Natale is going to offend someone by mentioning Christmas.... or if it is better to wish them "Happy time off from work"
Yes - I am most definately being cheeky and sarcastic in case you were wondering
Happy Holidays is very American...which may bear no importance to you at all. Season's Greetings is general, non-religious (if you're bothered) and used in Europe, Australia and USA