Hi E.! I am going through the same thing. I have a 2.5 yr old son too, and have been nannying for the last year so that I could be with him. He just started daycare again 3 weeks ago. He loves it there. The first 2 weeks were great, he didn't cry once when I left, and would tell me to go back to work in the afternoon because he didn't want to leave. On friday of the 2nd week, his normal teacher was on vacation, and there was someone different that he knew, but not as well. He got upset (he also takes a while to wake up in the morning, and on weekends wants to be held and cuddle for like an hour, so I think that also affects his drop off) Now all of last week too, he did the same thing. I feel bad leaving him, but I know if I stand outside the door, they crying usually stops AS I LEAVE. It takes about 10 seconds. He loves being there with all of the toys and other kids and stuff, it is very exciting, and I think that for the first 2 weeks it made him forget about me. But now it has become normal, not so exciting anymore, and he notices that I am leaving him. He isn't too busy playing to care anymore, because it isn't so new and exciting. He is still very happy in the afternoon and doesn't want to leave, and on weekends will wake up and ask to go to "school", so I have no doubts about the care he is getting. I have worked in a daycare and had bad experiences when I was a kid, so was very picky about where he went and toured everything. I know this is the best one I saw, and have a friend who worked there who knows his teachers and says they are amazing. Over time, it will get better. I just sit down with him for a minute every morning, get a toy and try to get him interested, but if it doesn't work, then I say "Ok, Mommy has to go to work. You be a good boy, I love you, and I will pick you up after your nap." He starts crying, the teacher picks him up, and as I get out of sight the crying immediately stops. I would not worry too much, they just spent a whole summer at home with Mommy, and now are going to a new place. That is very hard for a young child, they don't understand why they are there, or why Mommy has to leave. That would be very scary. Just give it time, and they will get better! Good luck!
J.