ACTIVISTS promoting sports for Hongkong's mentally handicapped children are backing Beijing's bid to host the 2000 Olympics. Regina Leung Wan-ting, sports officer of the Hongkong Sports Association for the Mentally Handicapped, said she would be looking forward to the benefits of a Beijing Olympics. ''I believe the greater interest in sports will benefit these children if Beijing can be the host,'' she said yesterday at the 17th Hongkong Special Olympics Swimming Gala, held in Kowloon Park. The event was held in preparation for the Special Olympics International 1995, likely to be held in the United States. About 500 participants aged seven to 20, suffering from mild to severe mental retardation, took part. They came from 22 special schools, day activity centres, and sheltered workshops. Urban Councillor Chiang Sai-cheong, officiating at the event, also supported the Beijing bid. Mr Chiang, chairman of the council's sports and activities sub-committee, said: ''To ensure that everyone, including the mentally and physically handicapped, has the equal opportunity to participate in sports is the core of the Olympic spirit.'' He hoped to see the spread of this Olympic theme in the region. The development of sports for the handicapped on the mainland was backward, Mr Chiang said, adding Beijing's hosting of the Games would mean a ''definitely positive'' prospect of sports getting more popular in Asia. He said many of his colleagues supported Beijing's bid for its benefits to sport development in Asian countries, and not for political or economic reasons. The International Olympic Committee will vote on September 23 for one of six cities including fore-runners Beijing and Sydney, to host the 2000 Games. Yip Wai-lun, 15, and Liu Yuk-yee, 10, of the Sha Tin Public School were two of the winners at yesterday's games. Wai-lun took the boys' 25-metre crawl-stroke, while Yuk-yee was the runner-up in the girls' 25 m flotation race. Both expressed interest in taking part in the 1995 Special Olympics.