Ive spent a lot of time behind the lens of the 90D and its a great hybrid camera, but the internal mic and handheld shake will ruin your footage fast. In my experience, you need tools that are reliable because weddings dont give you second chances. For audio, these are the two Ive used most:

• Rode VideoMic Pro+ Shotgun Microphone is probably the most user-friendly choice. The best feature is the auto-on function. It connects to the 90D and turns on when the camera does, so you never miss audio because you forgot a switch.
• <a href=" https://www.bhphotovideo.com/c/search?Ntt= Sennheiser+MKE+400+Directional+Microphone&BI=8941&KBID=10361&SID=2222&DFF=d50" target="_blank" rel="nofollow sponsored">Sennheiser MKE 400 Directional Microphone is another solid pick. It has a built-in shock mount and windscreen that are actually effective. I find the sound profile a bit more natural than the Rode. Stabilization is trickier since the 90D is relatively heavy compared to newer mirrorless bodies. You need motors that wont struggle:
• DJI RS 3 3-Axis Gimbal Stabilizer is the gold standard right now. It has automated axis locks that make traveling between the ceremony and reception so much faster. Balancing it is fairly intuitive once you do it a few times.
• Zhiyun Crane 2S 3-Axis Gimbal is a very capable alternative. Its built like a tank and handles the 90D weight without any jitters, though it feels a bit heavier in the hand after a few hours of filming. Personally, Id pair the RS 3 with the Rode mic. Its a professional setup that stays out of your way so you can focus on the shots. Just spend a weekend practicing the balancing act before you head to Seattle tho... wedding schedules are always tighter than they look.