The reason there are errors you can't reconcile is that this is not painted from life. This is a lady of 1850.
After this the hoop skirts only get bigger.
This is a gentleman of 1855, who wears trousers and a frock coat.
The people you see here are from decades earlier. The gentlemen wear swallowtail coats with breeches and stockings. The women wear the Empire waist, soft white gowns, and spencer jackets, with long shawls off their elbows, not big triangular ones covering the upper body.
In short, your Spanish painter was painting a scene out of the Napoleonic period, or shortly thereafter. The supposed queen wears the high waist, but her hair is that of before the Revolution, afro curls powdered over, while the "king" wears a powdered wig that would suit even the 1770s.
This means, depending on how good the painter's research was, he could have stitched together reference materials that were not compatible. This could explain the sash being the wrong side, besides the anachronisms. The women are mostly dressed 1810, with the queen wearing what is not really a walking dress, and lacking a bonnet. I would say she and the king are copied out of more official portraits.
At this point, you can only guess at what he was attempting to portray with his linseed oil time machine.Locating the structure in the back (I believe it is a carousel) will tell you where, though the guardsmen tend to indicate France -- but maybe not Paris. This could be a fantasy of Louis XVIII going for a stroll -- it needn't connect well with reality.
My three cents' worth, from studying the era 1803-1816, and training in portraiture, is that the king lacks the jaw structure of either George or William IV. He isn't Hanoverian.