''She was always afraid of the impact it had on kids,'' her son, Hamilton Meserve, the publisher of a chain of newspapers in Dutchess County, said yesterday. ''She was constantly trying to reassure children that this was make believe.''

Taught Kindergarten

Miss Hamilton was born in Cleveland in 1902, the daughter of a prominent lawyer. She wanted to be an actress, but her parents insisted she learn a profession by which she could support herself. She was teaching kindergarten at the Rye (N.Y.) Country Day School when she helped a friend audition for a part in the 1932 Broadway play ''Another Language'' and won for herself the part of Helen Hallam, a waspish wife.

A surprise hit, the play was made into a movie and became Miss Hamilton's ticket to Hollywood. In character roles in more than 70 films, she found herself playing a succession of stern spinsters, prim Yankee aunts or other unpleasant women.

She played, among other movie roles, a prudish busybody who detested Mae West in ''My Little Chickadee'' (1940); a reproving spinster in ''George White's Scandals'' (1945); a political boss's maid in Frank Capra's ''State of the Union'' (1948) and an ill-tempered dowager in ''Brewster McCloud'' (1970).

She frequently interrupted her film career to take roles in repertory and regional theater and played in the Lincoln Center productions of ''Showboat'' and ''Oklahoma.'' For 51 weeks during the mid 1970's, she played Mme. Armfeldt in the touring company of ''A Little Night Music.''