I see that there are overnight trains that do this route. But does it make more sense to just buy a separate Vienna-Venice ticket, and then a Venice-Florence? Or is it possible to get a 'flexible' ticket for the whole thing--ie one where we could get off in Venice for a day or so and then get back on. Does such a thing exist?
Well, there are exists a type of ticket which allows unlimited stopovers on the way, however it doesn't really make sense in your case, since it will be rather expensive. Much cheaper will be just to purchase first discounted (SparSchiene) ticket Vienna to Venice (from 29 euro when purchased in advance) and then get another discounted, but this time domestic Italian, from Venice to Florence (from 9 euro when purchased in advance). In total combination of two separate discounted tickets will cost you much less than standard fare ticket. The only inconvenience is that discounted tickets are for fixed train and date, so they make sense only if you definitely have the date you want to travel on
Discounted ticket from Vienna to Italy you can buy via
Austrian Railways (OeBB) website, while for Venice to Florence it can be
Italian Railways (FS) or private company -
Italo Also, it looks like Trenitalia has both "familia' savings (20-50%) and 'Bimbi gratis' (kids are free). I presume you have to choose one option or the other? Are there opinions on which make more sense.
Yes, relatively new offer "Bimbi Gratis" cannot be combined with other reductions, so it's either one or another. However again, it might make more sense just to go with discounted (Super Economy) tickets for all, meaning adults & children, instead of both group/family offers, because even buying additional ticket for your child can still be cheaper (obviously as far as you all travel with discounted tickets). Offers like "Family" or "Kids Free" intended for passengers traveling with full standard fare tickets