If you live in Dupont, I would suggest checking out Foundry United Methodist Church Christmas Eve Service. It's at 16th and P St NW.
They have an extremely kid-friendly, kid driven service at 6:30pm. The candlelight service is at 8pm. Kids are welcome at both (I'm taking my 6 mos old to the 8pm service). It's a great church, very welcoming with a vibrant pastor and staff.
You can probably walk there if you're in Dupont, but there's also a Colonial Parking garage on P Street (between 16th & 17th St)
http://www.foundryumc.org/christmas-eve-0
December 24: Christmas Eve
6:30 PM – Kid Friendly! Begin your Christmas celebration with festive worship. This worship service is designed for families and children. There will be music performances by the children, interactive storytelling and glow sticks for the kids.
8:00 PM – A time of Lessons, Carols and Candlelight. Join us for a rich tradition of celebrating with beautiful music, singing Christmas Carols, and a Christmas Eve homily give by Senior Pastor Ginger Gaines-Cirelli: "Word of Hope"; Luke 2:1-20.