I agree with the others who think it's best to speak to him face to face, rather than telling him in a message that you're feeling uncomfortable with all the attention/gifts. If he's simply out of practice, and trying a bit too hard to impress you, he may feel embarrassed, or offended, by being told he's made you feel uncomfortable. That would be a shame if he's genuinely a nice guy.
If you do want to message him before you go out for the meal, I'd keep it light-hearted, and simply tell him that you're looking forward to going out, but as you're not used to all this dating malarky, you'd like to take things very slowly, and just see where it leads.
You can tell him in person that there's no need for him to shower you with gifts, and messages, that you'd just like to spend time slowly getting to know him. Hopefully, he'll get the message, and he may even be relieved! Who knows, it may develop into a special relationship. Good luck!