Brighton - what to see with 2 & 4 year old?

[Calico1]

Hi - just arrived in Brighton for a few days. Can anyone recommend good things to do (indoors and outdoors) with a 2.5 year old and a 4.5 year old?

Pier, Aquarium (depending on your ethical stance) , Hove Lagoon if it is nice, Volks Railway, Marina (cinema, shops and eateries). Further afield Bluebell Railway, Drusillas, Lewes Castle