If you want a night alone then you should leave the kids behind, but if you would like them with you they will fit in fine.
Le Cellier has the "feel" of an upscale place, but really isn't.
Yes it is a small place the tables are close together, but no so uncomfortably close.
We seen plenty of kids there, well behaved and enjoying their dinners. It definitely is kid friendly, but the focus is on adults, not the kids. Where a lot other places are focused on the kids.
And just an fyi, depending on your kids Disney's is very good with the dealings with "strangers" as babysitters.
Remember Disney is kid focused. Can you imagine the back lash if these babysitters weren't use to dealing with "strangers kids". ???
Yeah they are prepared for that. So unless your kids have severe issues with being left behind I think they would do well.
But of course only you know your kids.
Have a safe and fun trip!