Name That Trauma:: Drew P. on a Evil Grandma Robot

Aloha!
I'm a longtime fan of Kindertrauma and I'm wondering if you can help me identify a particularly paranoid kids cartoon from a long time ago…

It would have been screened during a Saturday morning cartoon block on ABC or CBS sometime in the mid-nineties (probably no later than '96), but the animation looked noticeably different from other 90s cartoons, so my guess is that it was actually an older, eighties cartoon brought back for a rerun. I'm not sure if it was an animated TV movie or a standalone episode of a show. For many years, I assumed it was an episode of CBS Storybreak, but recent digging around online proves that this isn't the case.

The story was about two siblings (older sister and younger brother, I think) on summer vacation whose parents are hypnotized by a malevolent alien robot disguised as an old lady. The brainwashed parents tell the kids that the robot is their grandma or their great aunt. They tell the kids that the robot is going to be their babysitter for the rest of the summer and then they take the car and split, leaving them all alone with the alien invader. The robot forces the kids to do chores, locks their pet dog in the basement, and generally makes them miserable. I think the robot starts building a UFO (just like The Thing!) or some kind of device to summon an invasion fleet. The kids try to warn other adults, but (in true Bodysnatchers fashion) no one believes them. The robot may also hypnotize a few other adults. Kids are immune to the robot's hypnosis.

The robot has a vulnerability to water. When water is nearby, its eyes start to glow and it warbles "water…water!" in a creepy-sounding electronic voice. The kids ultimately defeat the robot by shoving it into a conveniently-located swimming pool. There's a big cloud of smoke and sparks, and then a satanic-looking face made of crackling red energy rises up from the bubbling swimming pool and flies off into night sky – presumably, returning to outer space, never to return. The parents return to normal with no memory of recent events. The dog is released from the basement. Everyone learns a valuable lesson that grandmas are pure evil.

Much obliged! Thanks for everything you guys do!
Mahalo!