@Bendy75 I was also widowed 6 years ago, so I know where you are. People do love to stick their noses in and say/ do the most inappropriate things.
I had terrible problems with some of my late husband family of origin, too. "Fortunately," for me being in my 50s, our eldest son took over and dealt with them.
Two of them are NC and will remain that way. Long story, but threats of violence aren't appreciated, and no, they didn't come to the funeral either.
Back to you, it's none of their business where you go and what you do. I advise you to tell them as little as possible from now on.
I suggest you say something like, "I hear what you say. However, we both are in m need of a break, so we are going. I understand you're grieving, too. However, I am only going for a few weeks, and I'll ensure my son is facetimes you or the like"
I suspect their is an element of control going on with them through fear, which plays a big part in grief. They may be scared of you being away so long, subconsciously thinking they are going to lose you and your son too.
You know them best as to whether they are just twats (like some of my late husband family) or this is newish type of behaviour.
Incidently, I got counselling through CRUSE U.K. It's a free non-profit, making service. You can ofcourse make a donation if you wish. I found it really useful. Link below.
It also helped me work through the dynamics of others and my late husband dysfunctional relatives. Granted, ours were at the extreme end however there services do involve talking about the dynamics around you too.
www.cruse.org.uk/get-support/