Here is the official word (at least as of May):
LUNCH: Guests may come in fashionable casual attire in order to enjoy the
Disneyland® Resort in comfort. However, no tank tops, cutoffs, swimsuits, bare midriffs, sweatpants, flip flops or beachwear may be worn. Walking-length shorts (knee length) are acceptable. Jeans are acceptable, provided that they cover undergarments and are not extremely faded or torn. Shoes are required to be worn at all times.
DINNER: If Guests have been enjoying the day in Disneyland® Resort parks, evening casual attire is acceptable for dinner.
For gentlemen, collared shirts and trousers are appropriate; for women, an informal dress or pant with blouse are appropriate. Jeans are acceptable, provided that they cover undergarments and are not extremely faded or torn.
Shorts, however, are not permitted for dinner.
CHILDREN: Appropriate dress for children and young adults is required.