Does selling food in a charitable platter to the needy and the afflicted, perhaps at a price higher than its cost, negate the sincere intention for Allah on the part of its purchaser, and is this considered an imitation of Christians?

This action is not inherently wrong; rather, it is categorized among the good deeds encouraged by Islam, as stated in the Almighty's words: "O you who have believed, bow and prostrate and worship your Lord and do good that you may succeed." There is no harm in adopting means that achieve noble, legitimate goals, as long as they do not violate the Sacred Law, for wisdom is the believer's lost property. And whoever undertakes this work should do so sincerely for Allah Almighty, because deeds are judged by intentions.