kayak for a 9 yr old

It looks like my daughters have outgrown their pink mini X.  They are complaining that it's too slow. 

I haven't been in the market for a kayak for probably 10 years, so I need some advice and recommendations. 

I'm looking for something that is agile, responsive, probably no more than 12'.  Fast for it's length is a plus.  Some stability as I hope to have at least one of them dive out of it in the near future. 

Thanks,
Nate

How about a T11