Whilst I can't comment on which open day you should try and attend, I urge caution for when you do attend. The aim of the organisation is to take your money from you. They have no interest in you....only your money. They will assess you and heap praise upon you and how suitable you are for a job in commercial aviation. This is what they do. They are a business and nothing else. They are your enemy!! Please do not get suckered in to something that you haven't had the time to thoroughly consider. Discuss everything with your family and ensure that you have a family member with you during any assessment and subsequent appraisal.
I wish you the best of luck but keep your eyes and ears wide open.