Worms will be fine with them. Worms generally like mycelium-heavy stuff, the mycelium has started the work of digesting/breaking down complex compounds for them. They might like the mycelium-heavy stuff a lot more, actually.

As with anything new or specific to feed worms, exercise caution and don't add a huge amount of one specific food at once, and be sure to add bedding at the same time. If you add it to one section of your bin, they'll avoid the stuff they don't like until it's ready to eat; the extra bedding gives them somewhere to retreat to (amongst other things).

I agree with armoured that it will be fine in the bin.

Can you post a link to this project I'm really curious about growing mushrooms with used coffee grounds. I agree I love mushrooms and having fresh ones every day would be fantastic!