I’m not qualified at this point to do translations, as unfortunately I haven’t studied the languages enough to be comfortable with the grammar and conjugations.
However, since this is a very popular quote, it has already been translated to Sindarin by others much more knowledgeable than me! So, in Sindarin, ‘Not all those who wander are lost’ is Law pain i reviar mistar aen, and would be written:
The quenya word for moon, as we know from names such as Isildur, is isil, written as such:
And lastly, a simple ‘Celine’ transcribed to tengwar:
Hope this is what you were looking for!