Bear with me cos it's a long one 
I've been with my Fiancé a little over 4 years now. At the beginning I really got along with my mother in law and the rest of his family but ever since we moved in together after being together 18 months things have really changed. While we were saving for a house I came home to find her going through my bank statements, they have a key to out house for emergencies but used to regularly let themselves in leading to some embarrassing situations. When we got engaged and started planning our wedding she made a guest list and seating plan without consulting me and invited people go I am yet to meet even after 4 years of being with my partner. It really got bad after I got pregnant with our DS, she works in the hospital and was changing my appointments to suit herself so she could come, she booked me in for a 4D scan which I had made clear several times I did not want and signed me up for parenting classes I knew nothing about. My DS was born by emergency C-Section 6 weeks early so had to spend some time in the NeoNatal until as he had problems with blood sugar and only weighed 2lb 9ozs. As I said earlier my MIL works in the hospital and I later learned she had tried to visit my DS to hold him before I had even held him. She completely ignored visiting hours despite me speaking to her several times and her reply was "visiting hours don't apply to me" which caused problems between me and the other ladies on my ward. Whenever any of my family or friends would visit DS at hospital she would make them feel uncomfortable. When we came out of hospital DS was on a strict feeding schedule, MIL used to pop in at 5pm when I had just put baby back down and was trying to get Fiancés tea ready. I calmly and politely told her that 5pm was an awkward time could she possibly go home and have her tea and come back at 7 when he was due a feed next and she could do it. This resulted in my being slagged off to entire family as she told everyone I had refused her access to DS. She questions everything I say about DS, I had some concerns about the size of his head and she kept telling me I was a bully and being mean about him, a doctor later confirmed I was right, his head was slightly to big for his body and he had to have some tests, thankfully it is due to his growth restriction in the womb and he is now very much in proportion. The final straw came when I was compared to a woman known to the family who abused her children leading to their deaths, I exploded with rage and she argued back saying she didn't mean I would ever harm DS just that she will not have her time with her Grandson controlled by me. I have explained to her how I grew up in an abusive household and how much her comments have hurt me, she refuses to apologise and has said that I should actually apologise to her for misunderstanding her. I have since refused to spend time with my fiancé's family although I have never stopped them seeing DS, last week my fiancé went on holiday with his family, me and DS didn't go, it was my fiancé's choice not to take DS. Trying to please fiancé I invited in-laws for tea the night before holiday, bear in mind they had not seen him for 2 weeks despite my fiancé asking, they turned up 2 hours later at 6.55 when my son goes to bed at 7pm. I was furious and did refuse them seeing DS, I felt like he was being treated as something to be checked off a holiday to do list.
Anyway to get to my question, since they have been on holiday my fiancé has Skyped us every morning and my in laws and his sister have been in the room during these calls and have walked past the camera without acknowledging me or more importantly DS. Now they want my fiancé to take DS to there house on Easter Monday to celebrate Easter but I'm really considering not letting DS go
Am I being unreasonable?