English Translation
We decided to plant all the trees all at once in a single day.
Is de un tirón perhaps a better choice than de a tiro? Wiktionary gives slightly different meanings.
https://en.m.wiktionary.org/wiki/de_un_tirón#Spanish
de un tirón
(idiomatic) in one go
Synonym: de un golpe
https://en.m.wiktionary.org/wiki/de_a_tiro#Spanish
de a tiro
(idiomatic, colloquial) totally; absolutely; completely
Synonym: de todo punto