Older children's book about two kids who have a magic spoon and fork that becomes a Spade and Trident (?) when they go into a fantasy world

Unfortunately most of what I remember is in the title.

There were a girl and a boy main character.s I seem to recall something about a massive frog or toad?? They used the fork as a weapon, especially. I had to have read this probably 20 years ago, but it was easily way older than that (it came secondhand from someone.)

All I'm seeing is picture books and that's not it at all. This was a novel for middle-grade probably, it had chapters with occasional ink illustrations. Not massive in length, but definitely not short either.