I would like to ask, at 24.12.2012 all the museums will be closed or there is a small hope some of them to work until noon?
24th is a Monday, lots of Museums in Hungary are shut on Mondays, including the Skanzen at Szentendre.
Suggest you check with the website of any other specific place you have in mind.
Since this is Christmas eve, the odds are that much of the town is closed. We were there last week and the owner of an antique shop was shutting down at the end of the week since "the season is over".