Mistake on submitted UK Spouse visa application

Hello. I made a stupid mistake on my wife's spouse visa application, its already been submitted and her bio metrics taken this week. I am going to submit the supporting evidence next week. I have read elsewhere on this forum some people have had some luck in printing the application form and making the correction in pen, and then writing a cover letter to explain the mistake. I've got the citizenship of her parents wrong and one date of travel. Has anyone had any experience of this? I'm hoping it not a reason to refuse the Visa if I point out the mistake? Thank you in advance!

There is no longer practice of sending documents by post to sheffield rather you have to scan, upload and dispatch them electronically through VFS centre. Ideal is covering letter which may work.

Thank you for your reply, its very much appreciated. Yes, I was thinking I would ask my immigration lawyer to write a cover letter (they have already written one to support the application) so I will speak with him on Monday to maybe add this or write a separate one. I will print the application, make the corrections and submit this with my evidence at the VFS centre then and cross my fingers. I just didn't want to get banned for 10 years for supplying misleading info. Thanks once again for taking the time to reply. Cheers.