（子供に）こっち見てねーって英語でなんて言うの？

These are very simple ways to say this. You can say them easily and quickly, and they are easy to understand.

1. You want to attract the child's attention. You make strange noises and jump up and down, shouting: "Look at me! Look at me!"
   2.Watch the birdie! - The phrase watch the birdie is an instruction given by a photographer to his subject, usually a child. Early photographers would hold a prop above the camera in order to gain a child’s attention, enabling them to photograph the child’s entire face. Often, these props were toy birds that would flap their wings or warble. In a time when children’s toys were simple rag dolls or marbles, such a toy would be a marvel. That moment of surprise was designed to stun the child into stillness, giving the photographer a chance to snap a crisp photo. Shutter speeds were much slower in the early years of photography. Today, photographers use a variety of toys to enthrall a child into sitting still for a good photograph. The phrase watch the birdie is now usually used for comic effect.

These are all perfectly acceptable ways to get a child's attention when you are trying to take photos of them.
Also,depending on the relationship you have with the child you may use terms of endearment such as "

Honey
Sweetheart
Cupcake
Angel

We would say " Over here!" in a louder voice to get them to look in the directions we desire them to look.

sometimes when trying to get attention from someone you could

"Look over here"
or
"and pose"
or
" say CHEESE" when taking a picture

*Photographing Toddlers. -Babies/Toddlers lose concentrate quickly and they can be a handful, so when taking them photos you need to get their attention. You can hold their favorite toy in front and call their name then capture the picture if possible.