My guinea pigs are crying for their veggies!?

I normally give my piggies their veggies at night, but seems it is the holidays, I have decided to give them veggies in the morning until the holidays are over (which is 2 weeks). Right now they are down the bottom of their cage, squeaking for their veggies! Will it be ok if I give them veggies in the morning even though there're crying?