Hi,just want thoughts on how suitable a sleeper carriage is on the polrail overnight train from krakow to Budapest is for a family of 2 adults and baby (10months)?
There is no such thing as "polrail overnight train". Polrail is not a train company, just a travel agency selling tickets for trains operated by railway companies. Your train will be operated by PKP Intercity (Poland) or MAV (Hungary). Polrail adds its service fee to the ticket price. In case of the overnight train to Budapest booking through Polrail may make sense as those tickets are not available online.
As regards suitabiity tor a baby, you will know best yourself - just imagine you will spend the night in a tiny compartment with just place to enter, a small table, the lower bunk doubling as a seat during daytime, the upper bunk requiring climb on a small ladder. Depending on the ticket you book there will be either two bunks per compartment (so you would have the full lockable compartment to yourselves) or three. The toilet and lavabo will be down the aisle and probably there will be no shower on the train.