Yeah, my babysitting gigs never worked out too well because of video games and horror.
When the parent's asked what games we played, they looked as if they were gut shot when the reply was "BLOOD!"
And they say that movie "The Texas Chainsaw Masacre" (the original) gives the little kids nightmares.
In my defense, I explained to the kids that the effects were all fake before they watched it.
5 year olds have nightmares anyway.
Just kidding!
But seriously, little kids like cartoony type characters like the Mario Brothers thugs Mario and Luigi.
Cartoon characters have basic shapes and simple textures, so you could make your own custom models even as a beginner.
That way you can cutomize them to your specific needs, and in probably less time than it would take you to hunt down what you want.