The Alex Jones and Steve Jones-fronted series sees celebrities perform famous dance routines, raising money for the charity.
It's All About Amy star Childs explained that she and Derbidge, who recently confirmed his exit from The Only Way Is Essex, will be among those taking part in the series, which will conclude during Sport Relief on March 23.
"Last week, Harry and I had a meeting in London and I can now tell you we are taking part in Let's Dance For Sport Relief in February," Childs wrote in her New magazine column.
"I don't want to spoil the surprise and tell you who we will be impersonating, but it's going to be hilarious. Harry is a brilliant dancer, whereas I'm rubbish!"
Previous winners include double act Charlie Baker and James Thornton, Robert Webb and Rufus Hound.
> Fearne Cotton whips Jimmy Carr into shape for Sport Relief - pictures
> 'Blue Peter' Helen Skelton completes Sport Relief trek to South Pole
Watch Robert Webb performing on Let's Dance below: