There are a lot of options here, and Sirius doesn't understand all of them, even having had more exposure to Muggles than most pureblood wizards. But it doesn't really matter. He's mostly enjoying having the freedom to go where he wants and do what he wants. After twelve years in a cell in Azkaban, a year on the run, and months in moldering Grimmauld Place, freedom is concept he had almost forgotten.

Plus there's food, and he's not going to turn that down.

He spends most of the evening standing along the edge of the room with a drink in hand, just watching, though he makes a few trips to the food table as well. Where he finds something just out of his reach, and he could go around the table to get it, but what he does instead is pull out his wand and make the particular item that he wants float onto his plate instead.

He's been here long enough to discover that this place isn't like home, and he doesn't have to hide what he can do. He really is free.