Unlike the vast majority of the arm-chair experts commenting here, I two of my children actually were in the IDF. They are still dati. It was a positive experience for them and for others in their respective units. I believe it was a positive influence on their Avodat Hashem, and I say that with a smiling face.
I’ve written an answer to your post three times and all three times I’ve deleted it.
Kol hakavod to your sons.
I’d like to point out one thing in response to your comment: The fact that a person withstands a nisayon is not a heter to enter the nisayon in the first place. Nor is the fact that one person withstands the nisayon a reason to suggest that there is no nisayon at all.