Having been to WDW without kids we can certainly appreciate the sensitivities of adults who just want a relaxing meal without screaming children. Like a PP mentioned it is a long time for youngsters to sit still and keep reasonably quiet. We may give it a miss on this occasion. There'll be plenty more visits in the future to enjoy signature dining.
I appreciate your attitude BUT...
If you dine closer to opening time for the signatures, you will find that the Signatures are largely empty. At least we did when we went last June. This is also a time when many patrons go with children. At least, this is what we noticed.
You can be selective in your choice of Signatures and pick ones that have the opportunity for a natural stretch for young legs in necessary. Like California Grill and it's open kitchen, viewing deck, etc. If the kids DO get antsy, take a little walk around. OR, plan for it with a combined trip to the restroom. We were invited to check out the view at CG after we first talked with our server, so this is something natural and expected IMO.
Jiko also has a somewhat open kitchen in that the appies are prepared in the open kitchen. These things would give the kids something to look at. ALSO, the idea of going to Jiko and seeing what is at AKL can make for a combined evening.
I think that another good idea would be to PRACTICE the idea of going to a fine dining establishment. Have fun at home and mimic the idea of what you would expect in Signature dining. Put the linens on the table, have a multi-course meal, etc. Don't flame me, but often times, I think that we parents forgo some things that we don't need to just because it starts to seem too hard, when really, it isn't that hard at all. Make the most of the opportunity that Disney offers and expose your children to something different.