IMO, putting the clowns and anemone in a confined space together is a very risky move -- if the clowns aren't ready to be hosted, and touch the anemone they could get stung, and at worse get eaten. Granted the risk is lower with an E. Quadricolor, compared to with an S. Haddoni, but not a risk I would be willing to take.
IME, the best thing it time.