Looking for a book I read in the 90s or early 2000s

It was a middle-grade reader, I think. Kind of goofy and spooky, with monsters and toys that came alive. I specifically remember some army men coming alive to fight a monster. Pretty sure the protagonists were two siblings, a girl and a boy.

Any ideas? I wish I could remember more, I listened to it as an audiobook in the 90's or 2000's in the US, I'm pretty sure it was new-ish then so maybe published in the 80's or sooner?