Dynamic params to use with Data Explorer

Would it work to move the defaults into the query and use them as long as no date is selected? So, something like this:

-- [params]
-- null date :start_date
-- null date :end_date

SELECT id as topic_id, created_at
FROM topics
WHERE created_at > COALESCE(:start_date, CAST(date_trunc('week', current_date) AS DATE))
AND created_at < COALESCE(:end_date, CAST(date_trunc('week', current_date) AS DATE)+4)