First I would like to say thank you to all your replies. As someone stated, being the Mommy isn't always fun or easy.
The reason I put conditions on coming home, is that he is a kid for whom everything must be spelled out, in detail. Otherwise he tries to change things to suit him. I am usually very firm with my rules, if you stay home from school sick, or come home. No friends, 1 hour of tv, no video games. I will read to you, play a quiet board game etc... I just felt so bad this time because both he and his friend looked so sad.
I decided to not let him go outside, but I did spend some nice time with him working on a diorama for a class project. We talked about school, starting middle school, taking the bus etc...
Turns out, that he knew today was my last day off. For 11 years I have worked the 3pm-1130pm shift. I am switching starting tommorow to 630am-3pm. He is very excited and happy for the change because I will be home in the evening to make dinner and help with homework. However, I will not be home for school days off or if they need to come home sick. I work in the ER of a local hospital and I cannot just leave unless its a true emergency. I have made arrangements for my MIL to help out in these cases. She's a young Nana, only 54 and she does a lot of fun things with them, but shes not me. I think he wanted just one more day of the two of us (even though I have 2 other kids).