Honey, I doubt its because he's feeling abandoned - more likely he is just so happy that he's seeing his much loved parents and its the only way he can express himself at this age.

I totally agree with mel. DD did this when she was younger when I'd pick her up from daycare, exactly as you describe it. It's just him expressing how much he loves you & DH

DD did it for quite a while, I cant remember how long exactly but I do remember it going on for months. She did eventually stop doing it as she got older & now runs to me with a massive smile calling "mummeeeeeeeeeeeeeeeeeee" hehe

I could almost guarantee that he doesn't feel abandoned, I bet he's having the time of his life with all those little friends & all those activities all day long!