Its a Bank Holiday so lot of stuff is closed. Here is whats open, I think. A star (*) denote places that use the Paris Museum Pass.
*Cath�drale de Notre-Dame: Cathedral year-round daily 8am-6:45pm. Towers and crypt Daily 10am-5:15pm. Museum Sat-Sun 2-5pm. Treasury Mon-Sat 9:30-6pm; Sun 2-6pm
Tour Eiffel: Daily 9:30am-11:00pm. Fall and winter, stairs open only to 6pm.
Cimeti�re du P�re-Lachaise: Mon-Fri 8am-6pm; Sat 8:30am-6pm; Sun 9am-5:30pm
No Idea if its open on that Monday
Mus�e de l'Erotisme: Daily 10am-2am
Also Samantha brought up maybe seeing a show at 4pm.
Coppelia at the Opera Bastille!
Wikipedia Link