Best way to change values of a primary key referenced by many tables

CREATE TABLE my_user
(    id       BIGSERIAL PRIMARY KEY,    username VARCHAR NOT NULL UNIQUE
);

CREATE TABLE my_person
(    entity_id BIGSERIAL PRIMARY KEY,    user_id   BIGINT REFERENCES my_user (id),    name      VARCHAR NOT NULL
);

CREATE TABLE my_project
(    entity_id  BIGINT PRIMARY KEY,    name       VARCHAR NOT NULL,    created_by BIGINT  NOT NULL REFERENCES my_user (id)
);

CREATE TABLE my_company
(    entity_id  BIGINT PRIMARY KEY,    name       VARCHAR NOT NULL,    created_by BIGINT  NOT NULL REFERENCES my_user (id) DEFERRABLE INITIALLY DEFERRED
);

CREATE TABLE my_product
(    entity_id  BIGINT PRIMARY KEY,    name       VARCHAR NOT NULL,    created_by BIGINT  NOT NULL REFERENCES my_user (id) ON DELETE CASCADE
);