You can try the austrian öbb (which is the same like the swiss sbb/cff).

http://fahrplan.oebb.at/bin/query.exe/en?

But I don't know about group reservations. Maybe you can find it on the site, too.

Hey just buy ticket at the Prague main station- after you will get there, they have always tickets, and in czech crown is cheaper. Trust me, I am Czech, I' ve been travelling with the very same train 4 years minimaly.... It goes every two hours approx.

Thanks Sandra,

Even with our group of 8? As we have kids with us, we would ideally like to sit together. Do you know if the seats are assigned, or is it 'sit where you like'?

Yes, I am sure you will get to the train. There are reservations obligatory for the first class, for normal second class you can also reserve the seats- it costs around 5 euros more. But I don' t see it necessary as they have older trains with the departements- so you will just find one free departement for all the family- they have them as the first departements in the wagon. And as I told you, there is the train every 2 hours. By the way- for the groups,as you are 8 people they have some discounts. For the kids less then 3 years old you don' t pay.

Super! Thanks for the tip Sandra. Can't wait to visit your beautiful country.

Anyway with the children it will be very nice to visit mirror labyrinth http://www.1pragueguide.com/mirror-maze. And the black light theatre, they have for example magic circus show, everybody loves it...http://www.pragueexperience.com/places.asp?PlaceID=892 and you have to book tickets to go there, here: http://www.pragueexperience.com/theatre/theatre.asp?EventYear=2013&EventMonth=07

Here in this website you can easily find out the schedule of departure and arrival. You can buy tickets online and can book tickets for future as well.

http://www.czech-transport.com/index.php?id=345