Phrase 書いて みよう か な?

Hi,
Is the か な a grammatical term here, or is it referring to writing Kana (Hiragana & Katakana)?
What does 書いて みよう か な mean?

My understanding so far is: もう そろそろ 何 か 書いて みよう か な と 思ったら… If/when you think you’re ready to try writing something…
…書く 練習 を 始め ましょう 。…begin to practice writing.
Thanks for your help.

かな is like having an internal monologue with oneself. Almost like “I wonder” in English. It is a bit difficult to explain but I will try.
書いてみようかな- “If you think that if ready you should write something, let’s begin writing practice.” or in other words “When you are ready, you should write.”

Another example: 明日、雪が降るかな。- I wonder if it will snow tomorrow.

Check out the examples from this link too: Review and more sentence-ending particles – Learn Japanese

Hopefully this helps.

brilliant! thanks a lot too for the link!

so かな here is I wonder if…
I see かしら is also a very feminine version of かな. Interesting.