S.T.
A.,
In my family we absolutely recommend Peanut Butter (PB & Ellie's) Café in South West Portland. They offer healthy food in smaller sizes and a good selection of salads. Drinks for the grown-ups too. They're located right across from the Southwest Community Center on Vermont, near Gabriel Park. You can make a full afternoon out of this by visiting the park or taking a swim at the Community Center. Ellie's has a nice train table, a blackboard and just generally a nice family atmosphere.
Good cheer,
S.