It's lovely, and I'm so glad you finally have a name
We often call Rory by his middle name, Oscar, as does his granddad, but it isn't confusing any more than when we use nicknames.
I think that's adorable and a great compromise! If you don't like the double-barrelled so much though I'd just do Eliza Grace and still use Gracie. This reminds me of Teen Mom 2 with Leah's daughter being Aleah Grace but they call her Grace/Gracie. no different than a boy called John Thomas and going by Thomas or JT if you ask me. Love it!!
so glad you finalized her name!!
PS - love how their names have matching syllables too, whether intentional or not.