Someone has translated them all here. Full context here. Official IDF condemnation here. The t-shirts depicting a Palestinian child with a rifle in the cross-hairs of a sniper rifle says:
The Smaller They Are The Harder It Is
Another one reads:
"We Won't Chill Till We Confirm The Kill"
A reader writes:
The context for the "'Every Arab Mother Must Know That The Fate Of Her Son Is In My Hands'" quote is a perversion of a quote by David Ben-Gurion which translates roughly as
"Let every Jewish mother know that she has entrusted her son's lives into the hands of worthy officers."
This isn't only Israel violating international norms and universal human rights, but also its own past ideals.
There are similar and worse slogans on t-shirts across the Muslim world and in Palestinian and Arab and Iranian media that demonize Jews in foul and fouler fashion as well, of course.