The proud mum captioned the snap of Kai cuddling his younger brother Klay: “Our Big boy is seven today. Happy Birthday Kai, we love you xx”
Fans responded to send their best wishes to Kai on Wednesday 2 November - and also to point out the spelling mistake on the illuminated sign.
Coleen, who gave birth to her third son Kit in January this year, returned to Twitter later that day to explain the spelling error.
She also shared a collage of photos of Kai on Instagram, with the caption: “Happy seventh Birthday to our Kai. Have the best day, love you loads.”