japanese letter help please?

ひいおじさんとひいおばさん
今年もよろしくおねがいします。 しん年のほうふは日本語が上手になります。 私の日本ごは下手ですね。 おげんきですか。私はとてもげんきです。 いいてんきですか。 私のうちでたくさんゆきがありました。いま、たくさんあめがあります。 日本語のクラスはとてもたのしいです。先生はやさしいです。 あしたに日本語のクラスにもちをたべます。 おいしいです。 日本ごクラスが大好きです。


i know its not very good, and it sounds child-ish. i also don't know how to end it.
also, i would like to change it as little as possible, so its still my letter, and i understand all that it says, but i would also like it to be understandable to japanese speakers.
thank you!
oh, also, please point out anything that is rude, i still haven't learned all the cultural aspects of japan.

There are several mistakes, but everything is understandable and well written and nothing is rude.

About the ending, why not write something along the lines of "Take care." or "Hope to see you soon."? I think you can come up with good Japanese expressions for those.

I agree with Uco-san that everything is understandable and nothing is rude, so you can send it out as it is. Very nicely written.

Just one sentence with very basic grammar that you might probably know:
あしたに日本語のクラスにもちをたべます。
This should be:
あした日本語のクラスで　もちをたべます。
"IN the class" should be "...kurasu DE."

Another suggestion, even though you might not know this sentence structure yet, to just help a little bit to make it easier to understand (though I understood what you meant perfectly):
しん年のほうふは日本語が上手になります。
To say "My resolution/ambition for the new year is BECOMING good at Japanese language," you say:
しん年のほうふは日本語が上手になることです。
...using the dictionary form of "narimasu," "naru" + koto.

I also agree with Uco-san that you can surely come up with good text for the suggested sentences :)