Invite a few kids of mixed ages you know. Welcome all of them with a birthday cap, A4 size paper, pen and pencil/ sketch pen, etc Before cutting the cake, ask them to draw anything about the birthday, and then proceed to the next room. In the next room, request them to sing a song and request them to praise each other. Before entering to final destination room where you keep your cake, display all of their recent drawings and invite one after another. They will be delighted to see their activities with your kid's celebration. Then provide a small gift to all of the kid guests and proceed to the celebration. There are many simple things you can do to make your day special.