Would we be able to go to Olomouc and or Trebon as a day trip from Prague?
Yes. It is possible to do it in both cases but IMHO it would be rushed. I would recommend overnight.
Probably possible but not very enjoyable. I would definitely recommend overnight. If you are confined to day trips only, do closer day trips or just spend more time in Prague.
Haven't been to Trebon but have been to Olomouc twice (as we loved it so much the first time). Definitely recommend that you spend a night there at least, enough to keep you entertained during the day, quaint theatre to visit in the evening and several good restaurants. This town is really very charming and much less touristy that larger towns&cities.Enjoy your trip.
Jo-Ann: It's possible in a day, but an overnight trip would be much better. I stayed in Trebon, and Telc and was much more enjoyable. There were so many more great places to stay and eat, and the people were much more accommodating in Telc. John