You want to turn your polygons into lines, make those lines be simple coverage edges, simplify those edges, then build them back up into polygons again, and finally use point-in-polygon to re-join the attributes of the old polygons with the new ones.
CREATE TABLE rings AS SELECT (ST_DumpRings(polys)).geom AS rings FROM polytable;
CREATE TABLE simplerings AS SELECT ST_Union(rings) AS simplerings FROM rings;
CREATE TABLE newpolycollection AS SELECT ST_Polygonize(ST_Simplify(simplerings, 10.0)) AS geom FROM simplerings;
CREATE TABLE newpolysnoattributes AS SELECT (ST_Dump(geom)).geom FROM newpolycollection;
CREATE TABLE newpolytable AS SELECT new.geom, old.attr FROM newpolysnoattributes new, polytable old WHERE ST_Contains(new.geom, ST_PointOnSurface(old.polys));
There are errors in the above, but the core concept is there. You can do it all in one query if you like.