I dont think you are being unreasonable at all given the history. Maybe it will only be aggressive towards other dogs but as a parent I can understand that its not a risk you are willing to take. I don't see a problem with you asking for the animals to be put away when you visit and if they decline thats up to them but you may have to catch up with them at your house or another venue. Its hard when its your paretns

Another thing is that I trust our dog more than I trust the kids which is why I dont like leaving them unsupervised (yes it happens but I try and avoid it). Kids do silly things sometimes, not trying to be nasty just not thinking and I dont think you can blame a dog for reacting if it is hurt by a child and depending on the age of the child they cant be blamed either therfore the resposible adult needs to supervise closely or keep the dog and children apart depending on the temperament of the dog and child