Use verb in -masu form + kana to wonder about something instead of using the -darou form

Question

The following sentence (in a context which is speaking about a woman):

青いワンピースを着て、どこに行くんだろう。

Can be translated as:

Where is she going in a blue dress?

Could I use「かな？」instead of the「ーだろう」form? E.g.:

青いワンピースを着て、どこに行きますかな。

Answer 1

青いワンピースを着て、どこに行きますかな。

doesn't sound natural (at least in modern standard Japanese), I'm afraid. The polite form of 「～だろう」 is 「～でしょう」. (行きます is the polite form of 行く, as you may know.)

青いワンピースを着て、どこに行くのでしょう。/ 行くんでしょう。
"I wonder where (she) is going in a blue dress."

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Using かな, you can say:

青いワンピースを着て、どこに行くのかな。

This would mean almost the same thing as your original sentence.