What is really wrong with this query please?
I'm not a MySQL expert, but it looks like:

SELECT CONCAT_WS(parent_title, parent_fname, parent_sname) AS 'Parent'
    CONCAT ('£1.50', sum(activity_price) AS Amount


should be:

SELECT CONCAT_WS(parent_title, parent_fname, parent_sname) AS 'Parent',
    CONCAT ('£1.50', sum(activity_price)) AS Amount


I added a comma after the first result column, and a trailing bracket to the CONCAT function.

While I have no idea if the latter concatenation is a valid operation, what I've suggested should fix the basic syntax errors.