I got an idea that might work better than a lot of electronics, and save you money.
https://www.stanwinstonschool.com/videos/make-a-monster-plastic-bag-technology
You could make the snakes out of long balloons, and attach the balloons to a bald cap/hat.
Have a tubing system attached to all of the balloons under the cap that wound run from a a hose to a " air bladder" you could squeeze air in and out of.
That would inflate and deflate the balloons = movement. The weight of the snake heads would make the snakes sway around/swing a bit from side to side.
That is just an idea though. I don't know if it would be as easy as it sounds, or even look good.
This might give you an idea of what you could do with animatronics if the other idea is not to your liking.
https://www.stanwinstonschool.com/v...cs-an-introduction-to-the-mechanical-skeleton
I have not tried any of the things in that video out, but I figure if you take apart a remote control car you can get a motor to work as a starting point to move the snakes.
The thing is snakes have such diverse movements that I cant think of a cycle for them to follow.
Most motions are built on pulley principles. In most cases these are in and out, left and right motions.
If you look closely at the first duck leg in the video. It is moving in and out.
The motor that it is running on is going around in a circle. that is because the pivot is at the end of the hinges arm, and that is attached to a arm that leads to the foot. The top of the leg never moves.
Maybe you could do something with that?
Maybe someone with better knowledge in animatronics will comment?
Good luck with your project.