My friend has just had twins and also has a 4 year old and a 3 year old.
Another friend (who I can't get in contact with) told me ages ago that she might be able to get some free (or subsidised) assistance like cleaners/nannies etc through AMBA if she has more children under a certain age.
I've called AMBA but could only leave a message and I haven't heard back yet. There isn't much information on their website.
Can anyone else give me some information in the meantime?