Your info at the moment does not really contain enough data to give a good recomendation.
Catamarans are available with two of the following three options
cruising load + toys capable
I agree with previous comments that going with a state room option and converting a boot cupboard for the youngest is not the best solution. It will also mean that you would soon have to buy a new boat. I strongly recommend going with a four cabin and two toilet boat.
I like the looks and liveaboard
capability of the Privilege
range, and a 45 in this is a great boat.
A St Francis 44 will provide what you need, and the Knysa is also worth looking at.