Translation:He is happy that his children have known how to live abroad.
That's not English though. You'd have to say something like "have known what it is like to live abroad".
Since the perfect tense of sapere means learned rather than knew (to learn is a completed action while to know is not), the best English rendering is probably "He is happy that his children [have] learned to live abroad".
No English speaking person would ever phrase a sentence like this!
I can't tell whether it's trying to say the children "have been able to live abroad" or "have had the experience of living abroad". I suspect it is the latter since they've used "saputo".
The above translation is truly terrible.
How would one differentiate the sentences °He is happy that his children have known how to live abroad° and °He is happy that his children knew to live abroad°? They seem like they'd have the same translation to Italian but I feel like they have different meanings in English, with the first meaning °they knew, in their time abroad, how to live properly° and the second meaning °they knew to live abroad rather than to not live abroad°?