This is something that most providers struggle with.
Tom Copeland had some very interesting advice to simply revise your contract to include an annual price increase. Check that out here
http://tomcopelandblog.com/how-to-raise-your-rates-2
As far as closing for vacation, some years ago I made that change too. I simply issued a memo announcing a "policy change" which was also an amendment to the contract. Since its the beginning of the year that is plenty of notice. Check out this book from Redleafpress.org
http://www.redleafpress.org/cw_Searc...+care+contract.
Hope that helps,
Adrienne