We go to stocksbridge. They have an under 5’s session in the baby pool which is brilliant.
The training pool at aughton leisure centre is nice and warm (my 6 month old likes it). I've only been to lessons there but they have family swim sessions each day too.
Stocksbridge - quiet and warm small pool, rarely busy. But it's pretty far out. Otherwise, King Edward is good, but can get a bit busy with toddlers. Just depends on the day.