For your beauty and the beast au would Lance completely loose it after finding out Keith is shorter than him as a Human?
YES YES HE WOULD!
Well I imagine it either like this: After the spell is broken and Lance is all happy that Beast is alright and not dead they kiss each other and the castle and the stuff turning back to normal. SO and they go towards the others, smiling and everyone is happy about being human again. And Keith is hugging everyone and Lance is still smiling. And they get married after some weeks and dance the famous dance again and while they do so, Lance is like: “Wait … since when can I look over yoU?!”
OR he just realizes it after the spell is broken and they kissed each other. AND starts to laugh and Keith is all confused, till Lance makes fun of him but in a sweet tease way C: