If you are going to use a greeting for the whole season doesn't it make more sense to say Happy Holidays since Christmas is only one day and there are many other holidays during this time of the year?
Why aren't you upset that Walmart employees don't say "Happy Chanukah"? Do you think Walmart has a problem with Jews too or do you think that Christian holidays should be treated differently than other religions?
Kids can't pray or carry a bible in school? That doesn't seem right as long as they aren't disrupting anyone or being sponsored by the school. Do you have a source for this? I've never heard of this being a problem unless a student is trying to preach to others or otherwise disrupting the learning environment.