Replace Hungarian with Spanish and you and I are in the same boat...
Here are things to consider
Search Picasa web albums, scribd (for example for you: http://www.scribd.com/doc/8255082/Crossword-Months-and-Days-English-Hungarian). Also search ESL websites, Google searches to consider: (grade level) worksheets (eg: preschool spanish worksheets), also add the hungry suffix to google (columbia is co...hungry looks like hu) and search for worksheets there.
Also...will this help? couldn't read it...http://www.magyarora.com/english/worksheets.html
here I can't read this: http://otthonoktatas.lap.hu/ (does that help?)
convince your librarian to get a grant to put in or expand their children foreign language books to include Hungarian books. Also see if Amazon has any books. Also, if family or friends are still in Hungry
the other part is to, well, create your own curriculum. It isn't as hard as it sounds...If you speak the language, just translate your own worksheets. If not, then hit up google and translate board books with a sharpie. It is slow going this way but it is going in the right direction. Also take the time to adjust your social studies curriculum to include hungry. Do up the holidays, food, landmarks, etc.
Also find bilingual blogs...if your lucky you'll find a Hungarian homeschooling blog. and that becomes your favorite website.
As far as the Hungarian educational style, well...here I must say, I dunno...try your best to teach, what, Russian, German, maybe some Finnish...
That probably doesn't help much...sorry
My life in emoticon...oh, I've said too much
As far as language we're going to be doing Spanish (their father's side of the family) and Hungarian, and German. Possibly some rudimentary French as well later on in high school. (I knew plenty of people in high school who were if not fluent then conversational in 4-5 languages, so it doesn't seem out of the ordinary to me.)
We're in homeschooling in Spain and don't use curriculum... My kids are little like yours, but so far it's been pretty easy to incorporate stuff across the board in our three languages. I think the most important thing would be finding sources (books, video, internet) to make sure you can continually incorporate interesting and stimulating things in Hungarian. If you feel a need for this to be more concrete or organized, maybe using something like a workbox system would give you an easy way to do this.
Other things that occur to me from my experience as a US student in other countries is that language is the most helpful tool for integrating, so I would imagine if your kids are communicating in Hungarian, they would have a big advantage in integrating into a school or peer group situation in Hungary. As an adult who's lived in foreign countries, I have also really begun to question the necessity of what is deemed "essential cultural knowledge".... My childhood passion for US history doesn't ever come up in life in Spain nor does my lack of understanding of the succession of Spanish kings or familiarity with the works of authors from the Golden Age. However, interest and curiosity about my adopted culture is always well received!
Maybe contacting with some European based groups would be helpful.... I'm so thankful for the ones available locally for me! Hungary isn't on this list, but maybe someone knows somebody... http://www.leben-ohne-schule.de/europa.html