Have they every tried using the wheel ?? Ever gone on it ?? When I got Holly she'd never known what a wheel was, I used to get her to sit on the wheel and then once she got used to that I would rock it a little and then eventually she started doing it. Also some wheels tilt forward which puts them off using it because they cant stay on it and others are fine.
As for toys not every hog plays with them. Soecially in front of people. I hide insects under them so she has to do something with them to get the insect, but after a while she just plays with them herself. (Altho most her toys I've made so I get upset when she doesnt like them, so she plays with them more because she knows)