Yep, cliche as it may sound, a good attack means having the diaphragm set before the note is called for. A lot of push from the stomach muscles (lower abdomen) to get the burst of air.

If the saxes are getting it right, have them do it a couple times so the trumpet player hears it done correctly, maybe he can instinctively match it.
That has worked often enough..

I do not work here, but the benefits are still awesome
Make your sound your own!