Could you put ramps on the ends, instead of along the sides/paths?
I'm impressed at how well toads can get up on things - I don't know how they do it. We even had one on our front porch because he wanted to sit under the air conditioner overflow water drip - our porch is about three feet off the ground. But I don't know how well hedgehogs can climb or jump. You might be able to make double-duty structures by putting small piles of rocks at the ends of the beds, so folks can either hide under the rocks or climb them to get into the beds.