We recently did a fun activity to pass off Wolf Achievement 8a. The boys really loved it.
Before the meeting I had printed off some simple pictures of several different foods that would belong in the different groups. I would give you a link to where I found them, but in all my searching, I could not find them again. I did, however, find tons of other images of foods from the different groups that would work, so you shouldn't have any trouble finding something that will work for you.
I also took paper lunch sacks and wrote the names of the different groups on them. These were then set up on a long table, and the boys lined up in two teams on the other side of the room. I handed each person at the head of the line a picture of a food, and then they raced down to the sacks and tried to put the picture in its corresponding bag. After the boys were done racing, we went through the pictures and decided as a group, whether or not the picture had been placed in the correct category.
This was way more fun for a group of eight year old boys, than just sitting and having a discussion about this stuff, and they still learned and were able to pass of the requirement.