The activity, booked through Mission, will promote Klass' Baby K range of clothing for Mothercare and Cartoonito's "Go and..." series of programmes for children up to six years old.
The campaign launches next Monday (19 October) and will include footage of Klass leading a group of mums singing "My Favourite Things" from The Sound of Music.
Along with on-air ads of the recording, 500,000 copies of a DVD containing the Klass singalong and five episodes of "Go and..." programmes will be distributed to playgroups and nurseries across the UK.
The activity and video will also be promoted on mums' community Mumsnet, as well as other social networking sites.
Cartoonito is part of Turner Broadcasting, a Time Warner Company, and broadcasts from 3am until 7pm.