Don't change any of the structuring of the sentence when you answer, since this is part of an assignment.
It currently reads as such:
Instead of your peas and carrots, I'd eat my way through a juicy lamb.
Do I use that, or
Rather than your peas and carrot, I'd eat my way through a juicy lamb.
It currently reads as such:
Instead of your peas and carrots, I'd eat my way through a juicy lamb.
Do I use that, or
Rather than your peas and carrot, I'd eat my way through a juicy lamb.