I think small fights are fine. My FIL once said something to me and Dh when we had a small snap at each other. oh don't be like that in front of the kids. I replied with, I think it is healthy for kids to see that we as adults can be frustrated with each other and have words yet still be in love and act like adults kwim?

We rarely fight/argue anyways but if we do yes we do it in front of the kids because I do believe it is good for them to see. Obviously bigger discussions aren't done in front of the children.