Welcome to BunPro!
You have a pretty good sentence here, but I noticed you misused the grammar point 「てからでないと」。The issue is the final part of the sentence,
When using 「てからでないと」、the phrase/statement has to be a negative. Right now, the sentence sounds like “If (you) do not dry (your hair) using the hair dryer, (we) can go out.” as opposed to “If (you) do not dry (your hair) using the hair dryer, (we) cannot go out.”
An easy solution to this would be to change
「出かけます」→「出かけません」
Can go out → Can’t go out.
I had to research a whole new grammatical term I haven’t learned to understand this, so I hope this can help you on your learning journey as well!