Just wrt Japan - pretty much everyone speaks english ( they learn it as a compulsory subject from primary school through uni)...certainly all the staff in hotels and major tourist attractions apeak it. and train system is excellent, although very crowded so a carrier would be best over a pusher.
Japan is an awesome experience, just be careful what ou eat if you are pregnant
Plus it is a non-stop flight to Nagoya and Tokya too from melbourne (about 10 hours or so) and only a 1 hour (behind) time Difference, so it probably wont be too unsettling for Zaccie's routine. AND he will love it - all the people and lights and smells and colours - very colourful!! - he will think it is just wonderful
so I reckon you should go for it!