[Nagoyankee]

Originally Posted by edG

I wrote "おてがみありがとうね。" to thank them for the notes first. Would "tegami" be appropriate? Most of the messages they gave me where just little notes or small decorated letters. Also would the "ne" at the end really be appropriate? Also how could I say thank you for the letter and picture (drawing) instead?

With kids, you can use おてがみ even if it consists of one phrase.

Go ahead and use ね, but do drop the う for the best balance with the casual ね. Keep the　う if you aren't using the ね.　

Letter and drawing: えとおてがみありがとう。

Originally Posted by edG

Next does this make 100% sense? "えいごがすきになりましたよかったです。" (to say I am happy that you started to like English)

Close! すきになりました　＞　すきになって or すきになってくれて

Originally Posted by edG

Also "えいごがたのしんだよかったです。" (to say that I am happy that you enjoyed English)

Same mistake as above. たのしんだ　＞　たのしんでくれて

Originally Posted by edG

Also "いつまでもがんばってください。" (Please always do your best)

Perfect.

Originally Posted by edG

Also "バスケとおにごっこをしてくれて、ありがとう、とて� �もたのしかったですよ。" (to say thank you for playing basketball and onigokko with me, it was lots of fun)

Nearly perfect. The first と ＞　や (assuming you played other games as well. If you only played the two mentioned, your sentence is perfect.)

Originally Posted by edG

Also "わたしもにほんごをがんばります。" (to say I will do my best to learn Japanese too)

Excellent.

Originally Posted by edG

And "ありがとう、カメラマンをがんばります。" (to say thank you, I will do my best as a photographer)

Kinda slangy but okay. Kids (under 11 or 12) actually would say something like that.

Originally Posted by edG

And a more challenging one, one of my students wrote "外国の人にあたらせっきょくてきにはなしかけてみた� �いとおもいます。" and I would like to reply that it is great that he has found interest in foreigners. Or maybe any other suggestions for replies?

I'm not you but you could say 外国人にきょうみをもってくれてうれしいです, better yet, 外国のことにきょうみをもってくれてうれしいです。

Originally Posted by edG

And finally "しんせつなことばありがとう。" (to say thank you for your kind words).

Nearly perfect. Place を　right after ことば. Another way is to place a comma after ことば.