He's too little for games, he won't understand decorations or the concept of a birthday, and 30 people will be pretty overwhelming for him. Be prepared for the likelihood that he will need some quiet time or a nap, and that he will have no interest in sitting around with a group while opening a lot of presents. Just make it more of a simple family gathering than anything else. I don't think kids really get the idea of birthdays until at least 3 or 4. Sometimes we adults exhaust ourselves planning a big thing and then we are disappointed when the kid is cranky and overtired!
There is a great salad you can make that keeps well - use cooked ramen noodles (2 packs - without the flavor packet) and a bag of broccoli slaw, some slivered green peppers (or any other color), a little oil & vinegar, slivered almonds, craisins, and sesame seeds, and anything else you want to put in. It keeps well because there is no mayonnaise. You can make it the day before and keep it refrigerated.