It's really hard to say who is being unreasonable without seeing the behaviour in context.
If your lunch was dominated by managing the children's behaviour to the point of being unable to have a decent conversation your parents have a point.
This also applies if your children were shouting, constantly interrupting adults for the sake of it, playing around with their food for more than a few seconds, standing on their chairs, getting up and running around, helping themselves to things they shouldn't or wiping messy hands on furniture/walls/people.
If they were sitting fairly quietly, joining in conversations appropriately, for the most part eating politely and doing what they were asked, the spaghetti on the wall was an isolated incident and you only had to threaten to leave once to stop the behaviour, they do not have a point. Your DD may not have known that hold a piece of spaghetti against a wall in unacceptable if she has never needed to be told before. If she was attention seeking, already knew it was unacceptable and continued to do it despite warnings that is different.
A baby and two pre-schoolers must be quite a handful and I imagine if you're not used to it they can be quite exhausting. That is the nature of children that age.
If your parents have watched your children ignore you, be rude, disobey you and get away with it I would imagine they are very frustrated, not least on your behalf. If your children listen to you and respond because you are reasonable in your expectations of their behaviour, give praise and warnings and follow the warnings with sanctions calmly and consistently then your parents are being unfair.
I think if you sit and ponder what your parents saw happening you should be able to answer your own question.