这要看语境,我来罗嗦一把
如果对方问：你去哪儿吃饭
就应该说“I'll have dinner at home”
如果对方问：你待会儿要干嘛
就应该说“I'm going home for dinner"
如果是老妈问：你今晚回不回家吃饭
就应该说“yes, i will come back for dinner”