Before this question can be properly addressed, we need to know the answer to a question:
Do you, on the one hand, think religion is a stylistic/personal preference decision like favorite sports team or preferring domestic vs. imported cars? Do you believe that inquiry into truth won't lead you to any particular place?
Or, on the other hand, do you believe that you simply know the truth, and while everyone else calls those beliefs "religion" because of their content, it's not really a religion to you. Do you believe that honest inquiry will invariably lead to the important parts of what you believe?
(Note: I don't really think there's another option. If you don't believe your religion, how can it be your religion? And if honest inquiry won't lead to your religion, then why do you believe it?)
I suggest that if it's the former, you go with Rayne, MichaelF, or Hairy's replies.
If it's the latter, then act as though what you believe is true and treat it like every other thing you want to teach your child in life. Would you like your child to understand physics some day and be able to do advanced calculus? Yes, but you don't force him to recite equations or study graphs at 4 years old. Do you want him to understand sex and have a healthy relationship with it? Yes but you don't sit him down with graphic pictures and explain every detail or give him a demonstration. Instead, you wait until the time is right and you tell him what he is ready for at his level in terms that he can understand.
If you think that what you believe is the truth, then you're going to also think that honest inquiry into its validity is only going to confirm it. Thus you are not threatened by your child being exposed to other ideas. You should be interested in him being used to hearing all kinds of ideas and beginning to learn critical thinking skills.
I think the best antidote to error and to ensure "correct doctrine" is not restricting what one hears but hearing as much as possible, while having the correct tools to evaluate each new thing.
That's what we do in science, and that's what I think we should do with our religion. It's no threat to me to tell my son that some people believe the Earth is flat (I don't know if any do, it's just an example). Then we simply set about to figure out how we might determine the truth of that. It might be a long exploration before the final aha! moment, even years.
Putting blinders on and throwing him forcefully at your beliefs as if they were the only possible ones is not going to do the job properly, because some day your child will be out on his own. If he only believes what you teach him because his mind has been bent to avoid even considering anything else, he'll either never be a genuine follower because it's not his own (and isn't that what you want?) or he'll some day figure out how he was duped—whether or not the basic tenets of your religion are correct—and may reject it all simply for having been brainwashed.
Make your religion part of the fabric of your life. Live it unashamedly, but not ostentatiously. Tell him what you believe, but prepare him to ask questions, to think, to learn how to sit with uncertainty without it being intolerable, as long as he is not content to remain there forever. Create an environment of free inquiry, but lead at the same time. Note this is not the same as telling him he has to come to his own decision—of course he does. But that kind of communication almost puts it back in the Ford vs. Honda category. Instead he should just be free to explore, knowing what you believe and being taught how to question everything and arrive at conclusions himself. Trust the process. Act as though believing anything else doesn't make sense. Because that's what you believe. Right? Right?
If that's not right, then you do have no business teaching him your religion.
And no, I don't think you should force him to pray. Does anything in your religion say that praying at meals is required for salvation, or something? Then honestly, what a misguided and ludicrous idea. It's a tradition of yours that you hope he will follow. But isn't the real issue one of gratitude for and dependence on the provision of God? Do you think he'll learn those by being forced to pray? Does he even comprehend lack well enough to appreciate provision, even your own provision? My 5-year-old doesn't.
I guess a second "real issue" you might be interested in is teaching the discipline of prayer. But prayer is a communication vehicle for those in relationship with God. Does your son have such a relationship? Does he even begin to grasp who God is and what He's like? If your son had a Great Aunt that you forced him to write letters to because you hope him to have a wonderful relationship with her some day, but he's never met her nor received any communication from her at all, is that really the best way to foster the relationship you're hoping will develop?