Sorry I can't answer your questions about children. But here is a site with much information to download. Richard www.inyourpocket.com/Poland/Krakow

Had 10 days in Krakow in the summer with a seven-year old. Krakow is great for children, esp the dragon that lives by the castle! Well, there is a metal dragon that breathes fire every 3 minutes, and always a crowd of children gather round it.
We had an apartment just out of the old town by the river which was great - quiet, great view, and only 10 minutes walk into the centre.
There are very many churches which are richly decorated which children will enjoy (in moderation of course), and there are towers to climb (the one at St Mary's Basilica has a resident trumpeter who will pose with you for photos). There is a good zoo, accessible by a bus from the centre, and the Salt Mine at Wieliczka is a must visit, and children will enjoy it (mine did).

Eating out is easy and cheap, children are welcome everywhere, and tasty ice creams only cost 2 to 3 zloty a scoop (0.50 to 0.75 euro).

The only place I advise caution with young children is Auschwitz, which is otherwise an essential part of anyone's itinerary. If you decide to go, and children aren't turned away, you must exercise caution (some graphic details of atrocities) and consider the effect that bored children may have on other visitors who may have lost their relatives there.

I would be more cautious than Alec, under no circumstances would take children of that age to Auschwitz, and I would have reservations about the salt mine. Too many stairs to walk down and too long to tour for small children, otherwise I am sure you will have a wonderful time.

I would not recommend the Salt Mine for young children. There are 800 steps to walk down and 2.5KM to walk once inside the mine. The tour takes 2 to 2.5 hours. Much too much for 3 and 5 year olds.

They would probably like a fiacre ride, Underground Rynek (excavations under the Cloth Hall), the castle area (but I would not take them into the Royal Apartments or the State Rooms - nothing much for children there - perhaps the armory).

They can play in the Planty - the park that surrounds the old town.

Make sure they see the trumpeter from St. Mary's Basilica who plays who plays from the top of the tower every hour on the hour and then waves to the crowd.

There are tourist trains that go to several locations; they might like to ride in one of these and the adults can listen to the commentary as you ride along.

Take them to Kosciuszko’s Mound, outside Krakow.