Reading some of the responses, all I can say is seriously, whatever people. Yes you can teach him as his mom. But he needs social interaction with peers. It's 9 hours a week, people! You will hardly be sending him "away" or neglecting him....I think it would be great for your little guy to get some experience like that. At "preschool", they play. They sing songs. They meet peers and make friends. They come across pleasantries and happy things to enjoy, and they come across some unpleasant situations and learn HOW to navigate them. (That we need to share, and how to share, and how to work things out with the children on the playground, that we need to take turns, how to take turns, and that you do indeed get a turn, lol.....if a kid answers you in a way that is not nice, what that feels like with the safety of an adult that can guide them, etc, etc). Yes it's mostly the parents' jobs to do this, but sometimes they really need to experience it with peers, not just adults. Your son is showing interest in the "idea" of school and classes, but is unsure of himself and scared of the unknown. That is normal. I personally believe that hugging him tight and saying "it's ok, you don't have to enter the big bad world, you can stay with mommy" is not helpful. Instead, I hug him tight and say "You are growing up so big. You are a smart, funny, friendly guy and your new friends are going to be so lucky to get to meet you and play! I am going to pick you up at __ everytime. You are going to go play, learn new songs that you can teach me, play on the playground, have snack, etc. And I promise that I will always pick you up! I do not lie, do I? You are getting big, and you're going to have a lot of fun". Just talk him up, talk the school up, get his confidence (in you, your word, and in himself) up.
Ask your preschool what is allowed.....can you bring a backpack? I got my son a cool new Spiderman backpack, and a matching lunchbox and thermos for snacktime that flat rocked his world. He got it as a surprise present the morning we started "school" (he was 2 years, 11 months old). He thought he was something else with that! We got him dressed in his favorite outfit, I asked how he wanted his hair for his first day (he sometimes wants to look "like daddy", sometimes spikey hair, sometimes a fauxhawk, etc). Then we took a couple pictures of him all looking good on his first day, with his backpack and lunchbox. He had so much fun!
Another thing: do you go to church? You could start out with taking him to the children's room. You come back in an hour. So he kinda gets the idea that you can leave for a short time and come back, and all is well. Oh---and go to the library with him ahead of time. There are a million children's books (for kids, not the "boring" ones for parents) on going to school (favorite characters like Martha Speaks, or whoever).