To make itself competitive with the early morning news shows bowing soon on NBC and ABC, CBS has canceled the Monday through Friday edition of its long-running children's show "Captain Kangaroo" and relegated the Captain to weekend mornings, beginning in October.

The move is almost certain to anger the activist groups who protested when CBS earlier ousted the Captain from his long-traditional 8 a.m. daily timeslot to make room for an expanded version of the "CBS Morning News," which it sent into combat--so far, completely unsuccessfully--against NBC's "Today" show and ABC's dominant "Good Morning, America." The ratings of the transplanted, 6:30 a.m. "Kangaroo" were infinitesimal.

Robert Keeshan, who created the character of the captain and has played him on CBS since 1955, chose to view the change as a rescue from the dungeon of the early morning slot. "To paraphrase," Keeshan told UPI, "reports of the Captain's death are exaggerated. He lives on . . . I love happy endings."

The "happy ending" consists of "Kangaroo's" return to a one-hour format, as opposed to the current half-hour version; the program will be seen at 7 a.m. Saturdays and 8 a.m. Sundays. CBS also stipulated in its compromise agreement that Keeshan can produce up to five after-school children's specials a year, which was offered as compensation for the fact that he will be off the daily television schedule for the first time in his CBS career.

James H. Rosenfield, vice president of the CBS Broadcast Group, said in announcing the agreement, "Not willing to abandon our 27-year commitment to the program, we concluded that if we couldn't bring the children to the Captain, we would bring the Captain to the children." CBS News insiders had conceded long ago that the chances of their "Morning News" improving its ratings were all but nil if the other two networks each had head starts with early morning news shows that aired while CBS was offering kiddies the Captain.

Keeshan, while not speaking against his latest exile to a remote corner of the schedule, did say of all three networks, "We're being saturated with news . . . I think there's going to be a rash of suicides if people really listen to all this news. It's depressing . . . There's still a deficiency in children's programming . . . The networks are remiss in this area."

At least Keeshan will be more visible on the air than he was, and CBS will not have to suffer the shame of being known as a Kangaroo killer.

"Availability to children is all we've ever wanted," Keeshan said. "It's all I've ever worked for, and if this gives us availability, I'll be happy."