no, all clowns must build up an immunity to their host. the fry would be eaten by the anemone, most likely, along with all other tankmates (their parents and shrimp included). the fry wont last long in the display, they'll either be eaten or starve. there is no real way to stop a pair from spawning. once they settle in and become fully mature, they will, its just nature. the only adverse effect from this is really their added aggression and even with just a single clown, you will eventually end up with a similarly ill-tempered female.
as for multiple species- that will end with the larger, more aggressive specimen killing off the smaller. its really one same-species pair to a tank, unless the tank is several hundreds of gallons, filled with anemones and rockwork to break the line of sight.