I bought one of those VK units from Don M. I really need to get it out of the box and try it... lol

I hooked up the VK to the kb today, and it's going to work just fine for the mic, but I'm having an issue when I also plug my ipad into the aux in (on the VK) I get instant feedback, even if the volume is at zero. I'm looking through the manual, and doing some research on why now.
I found another shortcoming - the song mode only allows 99 MP3 songs, no matter how many you have on your disk. There may be formatting issues here, but I followed the directions, and formatted the USB drive in the kb first. There's 999 locations for saving user recorded songs, but I don't understand why it won't read all the songs on my flash drive. This is a first. It's not like they are loaded into the kb, itself - they reside on the USB stick. Puzzling.

I still like it alot, but I'm finding out what it CAN, and CANNOT do. It's a process, but either way - it's coming to the winery in July.
More info as I learn it.

The more I listen to it ... the more I like it.😎

Perform VK feedback issue update:

I'm still quite baffled that I can hook up the harmonizer to the KB aux in, and have no issues UNTIL I plug the iPad into the VK aux in. There's no logical reason that this connection should induce a feedback loop, but sometimes sonic gremlins defy logic. If I reduce the volume of the VK output, then the feedback can be controlled. Curious, and curiouser, right? This has all been preliminary testing in my studio, and not a practical hookup, which I'll try to do this week. I set it up as intended, and run a mini rehearsal to see whether its powers are for good or evil.

I did a lot of comparison research, and there is nothing in this price range that can do a better job, so if I have to make some concessions, then that's the plan. I need a light, small, quiet, all-in-one instrument for when the PA4x is a bit too much.
The Yamaha 410 was in the running, but the extra 6 inches makes it too long for all my cases. It also has wimpier speakers. This unit has to handle the kb, AND vocals without buzzing, or fuzzing.
The Yamaha 463 has no discrete audio outs without disabling the speakers. I need that monitor factor. The internal speakers will be 75-80% of the perceived sound in the room. I intend to bring an S1pro just for some added bass, and directionality.
I didn't include Casio because of SO many reasons .... mostly key flimsiness (worse than Yamaha), sounds and styles. (yup - that's everything about it)

Sooooooo, friends - my journey continues, and as I approach the destination (on stage at the winery), I feel more, and more convinced that Korg has a winner in this budget category. If the worst case scenario is that the accompaniment parts turn on each time a patter is selected, Korg has provided me with 2 handy buttons to shut off all the cheese in a split second. Not my first choice, but not a bad workaround. Sometimes, it's all about compromise.
There are a bunch of the great EPs I love in this board, and the drums sound fantastic, so add that to my vocals, and you've got a band.
(fingers crossed)

Why not the guitar rig w/vocals instead of KB just
for this small quiet gig..?

Two reasons ... this winery is an afternoon thing, and I'm already set up for work that evening at the restaurant. I don't want to tear down my steady rig.
The other reason is the intimacy, and fullness of the keys. With guitar, I rely on more tracks, and rhythm for the ensemble, but in this intimate setting, a keyboard affords me options that will be more pleasing at a lower intensity. Tracks are awesome, in the right setting, but the quieter you play, the less convincing the music sounds when it's prerecorded. MIDI, MP3, drum tracks - they all suffer when you're not pushing a little more air. I can also sing a lot less with the keys, because I can fill in melodies to rest my pipes, which is paramount with this season's schedule. Singing 30+ hours a week can take a toll, when there's no down time to rest.
My job at the winery is background, not showman, so I'll use the tools that best facilitate that.
Every job is different. I've never been a cookie cutter performer, and I think that may be why I have been blessed with so much work. I tailor every job to the client, the venue, and the moment.

I may need to issue a retraction about this statement.
I've listened to a few demos, and the sounds have definitely improved from everything I've ever played by Casio. The key feel is still an issue, so I'll try one out when I get home tomorrow, and tell you what I think. If it's solid, and tight, I may put it in the running.
Feature-wise, it actually might have more to offer, with the mic input, so my ears are open. Se shall see.

Dave, have you considered trying a small inline (headphone) volume control with the iPad? Behringer has 2 small models.