For changing money the best thing is probably just to use an ATM. There are plenty around.

I can't really help with the query about the children other than to suggest a visit to the donkey sanctuary.

If you are going in the summer there is a nice water park at Velez which is worth a visit.

Hi Lindafach.
There are plenty of local exchange offices to change your money,as i find the atm's can be tempermental.
The best beach for the children I would say is burriana it has toilets,showers,shops and some really good restaurants.
The donkey sanctuary is a great place to visit.
A day trip to Tivoli World at Benelmadena is worth a look.
Hope this helps.
Inz,