I think it depends on the age definitely. A younger kid, I do what cat herder said, just grab them :P
I had a 3.5yr old one year and he would scream and cling to mom. His 2.5yr old sister came in with no problems :P I would peal him off and set him next to the door. I told him he can join when he's ready. He would sit for a few minutes, and join no problem. I also sent mom/dad pictures of them playing happily
**Side question- Cat Herder, what do you do when kids turn 1, do they have to leave?
I had a 3.5yr old one year and he would scream and cling to mom. His 2.5yr old sister came in with no problems :P I would peal him off and set him next to the door. I told him he can join when he's ready. He would sit for a few minutes, and join no problem. I also sent mom/dad pictures of them playing happily

**Side question- Cat Herder, what do you do when kids turn 1, do they have to leave?
Comment