IMO it is up to you to make the necessary provisions in order to deliver your performance at show time. I'd bite the bullet and buy an amp. Then you can turn it up to the required volume in the rehearsal room and balance the levels of your patch changes properly.
I agree that you need a keyboard amp. It makes a sound guys job that much easier. I see all the amps as each musicians personal monitor, if I can convince the band to have a reasonable stage volume, the it makes my job easier. Keys are hard to mix, as there can be big differences between different patches, and how they sit in the mix.
I assume you've gone through all your patches, so they all have the same volume level, and there are no surprises out front. I seriously think a keyboard amp would help a lot. I do sound, and play in a band. Our keyboard player uses a small guitar practice amp. It's enough so she can hear herself, and then the FOH guy can mix her as it's needed.
I get lots of compliments from bands. Its a usual 3-4 mics, 2 guitars, bass, drums and maybe keys. When I'm setting up, I'll set a general monitor level for the mics, before the band arrives, then I know that much is good, and will need a bit of tweaking once the band sets up. I currently run only 2 monitor mixes (board limit) so the bass/drums share a mix, along with the other 2. So if the guitar and keys player are on the same mix, and the keyboard player wants more, it comes up in both monitors.
A keyboard amp would give you control on stage for the amount you need, and it could be added as well if the others want some. Luckily, that will change when my new mixer arrives in a few weeks. A StudioLive 24.4.2 which gives me 10aux outs etc etc. Everyone will have their own mix, and I'll be able too have up to 6 monitor mixes if needed.