We are also visiting in March for 6 nights and these are the resturants we have booked:
Manhattan Restaurant, Hotel New York
Buffalo Bill's Wild West Show (booked for the 9pm show on-line for 30 Euros)
Walt's An American Restaurant - Dreams! Meal
(booked this for 4.30pm to see the parade go past and to get a good place for Dreams! and the Welsh Festival fireworks)
Character Sunday Brunch, Inventions,
Disneyland Hotel
California Grill, Disneyland Hotel
Auberge de Cendrillon, Character Princess Meal
Would have booked the Blue Lagoon but it is closed when we are there.
We are also going to try these too if they are open for other meals and snacks:
Agrabah Café
Toad Hall, Fantasyland (Been told their Fish & Chips are nice)
Café des Cascadeurs (Always closed when I visit)
The Lucky Nugget Saloon
Restaurant Hakuna Matata
La Grange, Billy Bob's Country Western Saloon
Restaurant des Stars
Annette's Diner
Hope that helps.