Can we have brown rice or millets for dinner?

Yes, you can have any wholesome grain with a sufficiency of vegetables for dinner ideally by 7 PM. 

In case you get late in having dinner, it would be best to avoid having grains and have a veggie based dinner (soup, steamed or boiled veggies, salad), in order to give your body ample cleaning hours at night, as grains are heavy to digest.