Generate your SET ADD TABLE and SET ADD SEQUENCE slonik statements for initial subscription. This will only add tables with primary keys.

slony_set_add_table_sequence.sql

SELECT 'SET ADD TABLE (SET id = 1, origin = 1, FULL QUALIFIED NAME = ''' || nspname || '.' ||  relname || ''', comment=''' || nspname || '.' ||  relname || ' TABLE'');' FROM pg_class JOIN pg_namespace ON relnamespace = pg_namespace.oid WHERE relkind = 'r' AND relhaspkey AND nspname NOT IN ('information_schema', 'pg_catalog')  ORDER BY pg_total_relation_size(pg_class.oid) DESC;

SELECT 'SET ADD SEQUENCE (SET id = 1, origin = 1, FULL QUALIFIED NAME = ''' || n.nspname || '.' ||  c.relname || ''', comment=''' || n.nspname || '.' ||  c.relname || ' SEQUENCE'');' FROM pg_class c, pg_namespace n WHERE c.relnamespace = n.OID AND c.relkind = 'S';

Also important to check that all tables have a pkey:

SELECT
   n.nspname AS "Schema",
   c.relname AS "Table Name",
   c.relhaspkey AS "Has PK",
   pg_size_pretty(pg_total_relation_size(c.oid)),
   sum(pg_total_relation_size(c.oid)) OVER ()
FROM
   pg_catalog.pg_class c
JOIN
   pg_namespace n
ON (
       c.relnamespace = n.oid
   AND n.nspname NOT IN ('information_schema', 'pg_catalog')
   AND n.nspname NOT LIKE 'pg_temp_%'
   AND c.relkind='r'
)
WHERE  NOT c.relhaspkey
ORDER BY c.relhaspkey, c.relname
;