There is a noun (in the late 1930s text Etymologies)
maranwe 'destiny', and using
tielyanna 'upon your path' from
Unfinished Tales, we might get Neo-Quenya *maranwelya 'your destiny'.
As for 'choose', all I can think of at the moment is
essecilme 'Name-choosing', but one would have to guess at a verb in the imperative here, as it seems to me at least, that 'choose your destiny' should be rendered in the imperative.
Unless someone has another option for 'choose', or wants to extrapolate using
essecilme, it would seem easier to write this in English using an Elvish writing system. If you want help with any transcription into the tengwar I can only describe them however, referencing the chart in
Return of the King. I don't mind doing that but some who are less familiar with the tengwar names or shapes of the tehtar seem to find this confusing.
For
Quenya versus Neo-Quenya see
Elvish as She Is Spoke, here:
http://www.elvish.org/articles/