Pasta is a great bet, nice and easy and can be mixed with different sauces.
Gnocchi is great (dried not fresh), as it cooks really quickly and is filling. Mix it with a jar of pasta sauce, and even some sliced peppers and you have a nice fresh meal. I'd avoid pot noodles, instant cook stuff... at the end of a day of walking you'll appreciate something 'fresher'...
For breakfast, the cooked element can be a hot drink. So, a cup of tea or hot chocolate plus maybe some fruit or those pre-packaged crepes is nice. Ideally, porridge is best as you'll get the most energy.
Snack-wise try and avoid really sugary and 'junk food', it's nice but not ideal. Dried fruit is best, but maybe a keep a mars bar if you need a pick me up!
One thing I've found over my past few years leading DofE expeditions is that having good food goes a long way - no matter how picky you may be, plan a good menu and you'll thank yourself! Good luck!