According to the Disney Blog:
Cost is $27.99, $13.99 ages 3 to 9. Hours are 5:30-9 p.m. nightly. For reservations, visit Disneyland.com/dine or call 714-781-DINE.
It also depends on whether you planning on going for breakfast (Surf's Up with Mickey and Friends) or dinner. Both are buffet, but breakfast features characters and dinner does not.
wdwinfo.com has the following prices (but no date to indicate how new/old they are):
Character breakfast: Adults: $33.00, Children (3-9) $17.00
Dinner: Adults $27.99, Children (ages 3-9) $13.99.
I would call Disneyland Dining and see if they can give you a more accurate/current pricing.
Our Authorized Disney Vacation Planners are here to provide personalized, expert advice, answer every question, and uncover the best discounts.
Let Dreams Unlimited Travel take care of all the details, so you can sit back, relax, and enjoy a stress-free vacation.