What steps do I need to take to apply for a Special Tourist Visa to Thailand with my spouse, and what documentation is required?

Hi all, I have a condo in Bkk where my son and his Thai wife live and I wish to go visit them with my wife on a special tourist visa for 90 days in December. Do I need to book (and pay) for the flight, insurance and quarantine hotel before applying for the visa and the coe/pass? I have started applying for this visa online. I have come unstuck on certain things - it asks 'Applicant's spouse (no age specific) or children (age under 20 years old)' and says to drag and drop file or browse from computer? What do they want me to upload? I have tried uploading a page of my spouses passport but it won't let me? I have uploaded my condo ownership document as the proof of my stay during the '90 days' and also for the 'after 14 days quarantine". I have used bank account as proof of residency where I am applying from. If anyone has recently been through this process and successfully had their visa approved (and their coe) - would like some help. Thanks in advance.