Hi - I'm a single man in my 40s...please feel free to show my advice to your husband:
Dear Husband,
I think going on a 4 month holiday on your own is a little unfair on your wife. When one agrees to get married, and then have children - that is a major undertaking of responsibility - to take care of your wife and children 'til death do us part'.
It means that from thereon - both the husband and wife - are required to make decisions which take into account the whole family - not just themselves.
If you are keen on travelling for 4 months of your gardening leave - your wife and children should come with you. I'm afraid to say it is highly irresponsible to take off on your own leaving your wife and children behind.
Even though you are the bread winner - the house and children are just as much yours as they are your wife's. A married man should be thinking about 'US' [your family' - not ME [just yourself].
I hope you won't abandon your wife and children - but instead take the family with you on your holidays