It's a hard one. Sometimes I can do two things at once- eg breastfeed dd3 and read a book to dd2- other times I explain to older dds why they have to wait or dd3 goes in a sling so I can do things for older two dds. Sometimes I can manage by predicting needs. Eg make lunch for older dds knowing dd3 will need to feed soon and I'll be unavailable to get food for them if I leave it any longer. Having said that... It's not possible to keep everyone happy all the time. Sometimes someone ends up crying!