I think weight well is a better option but you may try this to make face slimmer...
Put one finger inside ur mouth and suck it hard for 10 secs than take out, repeat it for 5-10 mins. This will make cheeks and lips less puffy and help looks slim.
Try bending your head back as much as u can until u experience a pull on the neck muscle. Then move ur lower jaw to and fro. You can feel pull from the neck muscle. Do this 4-5 times daily for around 2-3 minutes. This will help your face look slimmer.