Anything free/cheap to do or see in Coventry with a toddler?

[BertieBotts]

Preferably close to the city centre, as we'll be travelling in by bus. Meeting my sister there tomorrow and have just realised DS is a bit old now to be happy being pushed around the shops.

Just a park or anything you could recommend would be good, or anything more exciting :)

Transport museum (right by the bus station) always a big hit with my DS. Sorry, can't remember what it costs to get in. Best park is memorial park, but that's another bus ride away. Cathedral is a huge empty space for running around in.....