Keep in mind that Italian text tends to be inherently longer that the corresponding English one. So it’s a good thing to give the translators an idea of the space they will need to fit. But there’s no need to “kern” the text at this stage.

I would save the typographic fine-tuning until after the text is translated, especially since widows, rivers etc. will change when it's translated anyway.

I think your boss needs to just understand a little bit more about how translation works. Designing for another language is difficult enough to begin with, let alone trying to work out the finer issues with the text. I'd give the translators your general template, and possibly some guidelines for where you'd like things to fit. If you have it set, you put a lot on the translators--their jobs are hard enough as is, let alone with the stress of trying to fit something into your exact parameters.

Riccard0 also has a point: Italian text is going to look very different from the English text.

Concerning the actual translation:
1) If you need a very good Italian translator let me know and I'll put you in touch. Plus she's in NYC which is more convenient (not least ideologically :-) than Italy.
2) As Riccardo says Italian takes up more space on average (actually Italian isn't bad, it's that English is very compact) plus translation typically expands the text length too; so you're looking at around 15% more text. When I translated David Rault's Excoffon book* from French to English I tried very hard to be compact but I still ended up only slightly shorter (I mean even though English is more compact than French).

* http://www.adverbum.fr/roger-excoffon-rault-david-atelier-perrousseaux_o...

hhp

it's that English is very compact

Dunno about Italian, but in my experience as English-Arabic translator, my Arabic translation usually takes 2/3 the English text when using monospaced fonts, and even less with proportional fonts, but it might be also related to the fact that Arabic orthography omits the short vowels from the body of the word.

Arabic is indeed extremely compact (and as far as I'm concerned dropping short vowels when they're obvious* is a great thing). BTW, a great reference for this stuff is Sadek & Zhukov's "Typographia Polyglotta" - although you shouldn't get me started about its concluding paragraphs...

* And in a consonantal language family like Semitic they generally are.

hhp

I think part of the situation with Arabic is that its script itself is much more space-saving than English. It's much tighter than the Latin script as a whole.

It uses the vertical space much better, so needs less horizontal space (and in the process fits our retina's acuity better too). However for that reason it also looks small on the body; and in some contexts it's difficult to live with that.

hhp