He will be nine

My son will turn nine years old in a few days and I thought he will be ten already. I messed up my counting. I asked him last night how old he will be and he said ten. I am a terrible mama for forgetting his age. I even told one of the guy at work yesterday that he will be ten soon. He wants to have a birthday party and invite his friends, but I told him no. I told him it cost money. I just want to buy him a cake and have a burger and hotdog at home with family, but he wants his friends. So yesterday I made a reservation at one of the pavilion at the park and have his birthday party there. We have a small house for his friends to play so the park is a god idea. He is so happy and now I have to start planning his birthday and sending out invitations for his friends.