Are electronic signatures valid in Italy? Are faxed signatures valid?
Yes, they are. A simple email can also have legal value in Italy.
I'm not sure at this point if the client has access/ability to print, sign, scan, and email OR do their own electronic signature
I think that if the client has ability to receive your translation via email, they have a computer and probably a printer too. Nowadays, IT equipment is widespread in Italy
Is it inappropriate to ask the client to mail the signed document back if I send it via fax or email?
Sure, you can ask them. I think also the client would like to do it the simpler way.
Would it be appropriate to charge for the expense of faxing or mailing from my end?
Yes, you can charge them, but only if it's a client's demand to be faxed or snail mailed. IMHO