Genki 1, p. 246 Ex. VIIIA #17-21

１８。旅行期間は二ヶ月ぐらいです。The travel takes about 2 weeks.

　　　そこには二ヶ月ぐらい滞在するつもりです。He intends to stay there about two months.

１９。どこに泊まるのかはまだ決めていません。

２０。南極でペンギンと写真を撮るつもりです。

２１。たけしさんは今年の冬休みはどこにも行かないつもりです。

よくできました。

Genki 1, p. 246 Ex. VIIIA #17-21

(*1) Your sentence is grammatically correct.
        If you want to say that Tom was not informed of the place where he will be staying in  the Antarctic,
           you can say that "どこに泊まるのかは、まだ知りません。"
        Or if you want to say that Tom has not decided where to stay in the Antarctic yet,
           you can say that "どこに泊まるのかは、まだわかりません。" or "どこに泊まるのかは、決めていません。"

(*2) Your sentence is grammatically correct.
        "~じゃない" is comparable to spoken language.
        If you want to express that in written language, you can say "どこにも行くつもりはない。"

Hi, Eric! Since I couldn't find any mistakes, I'd like to give you additional information. I hope it would be useful in order to deepen comprehension of some words! Thank you! (*^-^*)/