Hi Val
The only country of the four to officially use the euro is Austria but you may find that the euro is sometimes accepted in the other countries. However, I would take the official currencies as it will be frustrating to have your euros refused in some situations. For Poland you will need Zloty, for Hungary the Florint and for Czech Republic the Koruna.
Have a great trip - it sounds like a fascinating tour.
Kind regards,
Olly, your editor