、？
Starting tomorrow, should we switch to something lighter like cornflakes?
Literal
Tomorrow [from-から] cornflakes [or-something-とか], light thing [to-に] do [question-ましょうか]?
明日から marks the temporal start of a change. コーンフレーク is the English loan. とか ('such as / something like') softens the specific example. 軽い物 ('light thing') uses 物 ('thing') as a generic stand-in for a category (here, food). ~にしようか is the volitional conversion ('shall we make it X?') — ~にする is the idiom for 'decide on X, settle on X.' A friendly, soft suggestion phrased as a shared decision.