it's low light. You know You're growing things in what amounts to 100% full shade. You clearly get it.. more would be better, and this is gonna be tough on your plants. You made smart choices in plants for this location, but you seem to understand they are going to grow slow and leggy. Really the only thing you can do is wait and see and decide how you feel about it.
The good news is there are tons of options for artificial lighting. You don't need expensive or ugly/industrial grow lights. Slimline LEDs could be relatively cheap to run And unobtrusive on the underside of shelves. Just make sure you're using a spectrum that will work for plants. If you're buying "off the rack", Look for 6500k bulbs.
Here's a 24w cfl just screwed into a living room light that's plenty for my aloe.. I ran out of window space, so it was this or freeze outside and it's working well. Ideally, if I were a grower I'd leave it on 16 hours a day. I do not do that. I'm not on a schedule, Honestly I have no idea how long I leave it on or when. Its pretty haphazard, any additional light is better than none.