We took our 2 children to our 3rd child's birth, they were just turned 3 and 4.5 years old. It was the middle of the night and the 3 yr old slept soundly through it all in the adjacent room (birth center like a house, door was open), just about 3-4 yards away from me in a recliner. The 4.5 year old stayed up the whole time and did wonderful! We had another adult there who was there solely for the purpose of entertaining them and meeting their needs throughout it all.
Baby #4, we had at home, we did not bring anyone extra on board to help with the kids. But it couldn't have worked out better. Kids were 6.5, 4, and 2 years old at the time. My water broke at 7 a.m. No contractions all morning, so we had time to get the house prepped and whatnot. Fed the kids lunch around noon, put the 2 year old down for a nap, started a movie for the other two, midwife showed up around 12:30, and real labor began around 12:45 p.m. He was born by 2:15 (yes, only 1.5 hours of labor!) before the 2 year woke up or the movie was over. LOL! The 4 and 6 year old came in to watch just as he was being born, then went back to their movie.
We're pretty much planning the same thing this time, with a homebirth. Although my mom may or may not be here to help out with the kids. I don't feel the need to have anyone extra around since it went so smooth last time. I will probably have someone on call for the younger two just in case things aren't going as planned or they're really in the way and I need them out. I think we did that last time around, but we didn't end up calling anyone.