Day in Cardiff with a 10 year old...not Cardiff Castle or Dr Who

[IToldYouIWasFreaky]

I am going to be in Cardiff with DS (10) next week. We're going to see War Horse and then have a free day.
Any suggestions of things to do? We have been to Cardiff Castle and Dr Who experience fairly recently so those are out and don't think I could persuade DS to St Fagan's though I think it looks great!
Needs to be city centre or accessible by public transport. Thanks!

Cardiff museum and Art gallery are pretty nice. The building itself is like a marble palace.

Techniquest! Then a wander over the bay to the Fairground on the Cardiff Bay Beach on the barrage.

Get the train to Caerphilly and see an old medieval castle

There's a beach at Cardiff Bay for the summer.
www.cardiffbaybeach.co.uk

Cardiff Museum is great a lot for a ten year old to see & do.
Techniquest is a nice train ride away in cardiff Bay & there’s a beach there at the moment.

Also Lego shop is in the city centre.

And another vote for Techniquest too.

st Fagans is amazing though and a brilliant day out.

Train or bus to Big Pit.

Train to Barry Island

White water rafting down Cardiff Bay.

Olympic size pool in Cardiff Bay with slide.

Ice rink in Cardiff Bay

Dr Who Experience has been closed for about a year anyway.

The museum has the Clore discovery centre which mine used to love when they were younger. Can’t vouch as to whether it’s still as good.

Some brilliant ideas thanks! DS would definitely be into Techniquest and white water rafting!