How long will it take on a normal Sunday (no special holiday or anything) to cover the Madame Tussaud's Museum?
Can we buy tickets on premise? Will there be a huge queue?
According to Google:
Sundays look busy in the afternoon, but free in the morning. You can buy tickets online for a 20% discount or get them on the spot. Unlike the museums in London or Amsterdam the Washington venue is not known for huge queues.