Sorry about the brief earlier post...I was going to say, "Try a clicker", and then the phone rang. Yeah, well, as you can see, baby is looking at her foot...mom is looking drowsy which makes me think mom is going into a blink, or coming out of a blink,while sissy is apparently looking at the photographer. For infants of the baby's age class, one of the easiest tools to use is a teddy bear, or a long, tickly feather, like a peacock, ostrich, or emu feather, or even a feather duster. The toy/feather/clicker method is of course, best for working on a tripod, with a remote release...you can tickle a baby under the chin or on the cheek and lean back toward the camera and then shoot...that will almost always keep all eyes on you.
The real underlying secret might be the idea that these types of shots are EASIEST to capture when shooting from a tripod or camera stand...you envision the camera orientation, in this case, horizontal, then pose the people to fit that camera orientation, then you frame, then focus. In your case, the background is clean and simple, and uncluttered, so framing is very easy and not super difficult to accomplish. With the camera FIXED in a solid position, then it's easy to use any number of methods to get all eyes looking in one direction. A remote release allows you to trip the camera without an obvious shutter triggering movement which will tip off people who are habitual blinkers. You can even use the remote and make a FAKE! fist pump and pretend to mash on the remote button, let them blink, then shoot after their eyes open. Blinking runs in families.
