Hmm... A dingo might work, depending on how close the plants are together. I would probably just do it by hand. I would use a pitch fork to get the bulk of it up, then use a shovel. You probably don't need to worry about making it look super clean since it's going to be covered with a new mulch. 80 sq feet is relatively small, so I would think two people could get it done by hand within an hour. One person should be able to do it in two by hand. Correction: I just saw that you think it is bigger than 80. Either way, I would still do it with a pitch fork then shovel. I would throw it in a wheel barrow and dump it in the trailer. With 2 people and 2 wheel barrows it wouldn't be too bad.