She might be the future Queen, one of the most well-known women in the world (and a former Brownie), but like anyone wanting to volunteer with the Scouts, she had to undergo a criminal records check.

The Duchess of Cambridge is to become a regular helper with junior Scout groups in London and north Wales after making the Scout Association one of the first voluntary organisations with which she will officially be associated.

St James's Palace said this means she will help to supervise games and other activities and probably go on weekend camps.

In contrast to the designer wear she is usually seen in, she will wear the standard uniform of polo shirt and scarf, secured with a friendship knot rather than a woggle these days. A supporter's polo shirt costs £14.30 and scarf £5.35, while splashing out on a baseball cap would add an extra fiver to the ensemble.

The Queen is president of the Scout Association and the Duke of Kent its patron – royal association with the movement goes back to before the second world war when George VI attended Scout camps and joined in their sing-songs.

Simon Carter, the Scout Association's spokesman, said: "The bottom line is that she wants to help on a regular basis and we are delighted. One of the biggest challenges for us is that we have 33,000 children on our waiting lists wanting to join and we need more adult volunteers to help. If someone who is high-profile and has a busy schedule is prepared to join in, that may encourage others to come forward to help too.

"There was no question of the duchess not having a CRB check and she has already done so. She will wear the uniform, but I don't think she will be given a name, such as Akela [the wolf pack leader in Rudyard Kipling's The Jungle Book], as group leaders are."

A royal spokesman said: "She will be assisting with Cub scouts and Beaver groups mainly in the north Wales area, because that is where she will have most spare time. It will be a regular involvement, as often as her other engagements allow."

Beavers are drawn from the six to eight age-group and Cubs from eight to 10.

As well as becoming a volunteer with the Scout Association, the duchess will become a patron of four other charities: Action on Addiction, which assists drug addicts and their families, the East Anglia Children's Hospices, the Art Room, which aims to increase children's self-esteem through art, and the National Portrait Gallery.

Graham Butland, chief executive of the hospices, said they were honoured to be chosen by the duchess. He said: "Having our work recognised in this way is not only a tribute to our staff and supporters, but a huge boost for the children, young people and families receiving our care and support." She has already privately visited one of the organisation's hospices at Cambridge to see its work.

The Art Room charity, based at schools in Oxford and London, works with children who are disruptive or withdrawn and need time away from full-time education. It aims to teach them life and interpersonal skills to boost their confidence and ability to make relationships. Its founder-director, Juli Beattie, said: "This is wonderful news. It is a fantastic endorsement of the work we do and the role that art and creativity can play in helping children and young people whose start in life has been difficult."

The palace spokesman said the charities had been chosen to reflect the duchess's personal interests in the arts, the promotion of outdoor activities and the support of young people. Several hundred organisations applied to be associated with her, but at least one of the chosen organisations did not do so. The spokesman said: "Action on Addiction was chosen because as she visited young people's charities almost everyone working in the field pointed to addiction as a major problem and she wanted to help highlight that.

"More organisations will follow but she has picked a few to start with so that she can get actively involved with them on a regular basis."

The duchess began researching possible organisations in the autumn and made her choices after meetings and making private visits. The charities are intended to complement her husband Prince William's own patronages of the Royal Marsden hospital and the Well Child and Child Bereavement charities. More than 30 organisations are now involved with the Princes' charities forum, set up by William and his brother Harry in 2006.