Hi J.,
My DH is a conservative Rabbi -- here's how we handle the night.
We start with the seder in the living room, sitting on the couch, throw cushions, etc. This allows the kids to get up and move around. Once you've recited the blessing for karpas, you can bring out as much vegetable nibbles as you like (I put out vege-based dips as well), which helps keep everyone going until you get to dinner. I noticed that Marcy suggested putting out Matzah crackers. Depending on your level of observation, technically you can't put out anything like this until after you've said Motzi, which comes immediately before you serve the meal.
I stock the room with symbols from the maggid (story) to encourage the kids and adults to ask lots of questions, and also offer candy rewards for good questions (you do have to be judicious with this, as some kids will catch on REALLY fast and ask tons of questions, just to get the candy. We keep the rewards small, like individual kosher for passover gummy bears). Some of the things I've put out in the past include a baby doll wrapped in a tallis and placed in a basket (Moses), covered the fish tank with red cellophane (Red Sea), sprinkled confetti stars around (G-d's promise to Abraham), placed a small box of sand on the table (crossing the Negev), toss out different things/small toys for the 10 plagues, etc. Sometimes I'll incorporate a game into the seder, like Charades, 20 questions or 10-plagues twister. This year we're going to make up "Jewpardy" (each category will pertain to a section of the seder). Basically, keep it informative, but fun and engaging. We prefer to ask questions and engage our guests in conversation and debate, rather than just go around the room and take turns reading the text. When my kids were really small, I made up felt boards that they could add pieces to, to help them follow along with the story. I also prepared them well ahead of time by reading them picture books about the holiday and singing seder songs with them (more on that later).
One thing that is important to remember is that you do not have to read every single word of the haggadah, although you do have to recite all of the blessings. Pick and choose what is meaningful to you and your guests. I often ask guests to prepare a little bit before hand -- either a question for discussion, a skit by the kids, make up a song, poem, or short essay, whatever.
Since the Torah teaches us that we all stood at Sinai, we weave in relevant current events to relate the story to modern times and issues. Many modern haggadot are very good at doing this. If you're still using the old Maxwell House haggadah, I suggest you invest in something more up-do-date (the MH haggadah is probably one of the worst ever written, IMHO). Two of my favorite haddagot are "A Family Seder" (comes in a version for younger kids and one for older tweens/teens) and "A Different Night." Also, the haggadah should be read in a language that everyone understands. It was originally written in Aramaic, since that was the common language at the time the service was ritualized, and some elements, such as the 4 questions, the halachma anya, and Chad Gadya are still written in Aramaic. So, it's OK to read even the blessings in English, if you like, or any other language for that matter -- as long as everyone will understand it. We often ask guests who speak another language to read some of the 4 questions in that language.
A big part of the seder is the music. I send out the seder music for people to learn the month before the seder, in case they're not familiar with it (I have it available for download from my sharesite. If you're interested, drop me a note and I'll make it accessible to you.)
Of course, the thing that all the kids look forward to is finding the affikomen. We break up the affikomen into as many pieces as there are children present, so that each can find a piece. Hunting is not allowed until we're almost finished with dinner, and everyone is allowed to find only one piece. A small prize is given to each child. When we have only teens at the seder, I make donations in their honor to organizations that support the ideals of the haggadah, such as a local food bank or Jewish World Watch, which supply solar cookers, healthcare, and education for refugees in Darfur. (I print out a tribute card for each teen). You can also involve the teens by having them hide the affikomen for the smaller children. We also ask one of the teens to sneak out the back after we've left out the cup of wine for Elijah, and dump the wine in the bushes. When the little ones go out to retrieve the cup, they get very excited to see that Elijah has actually "visited."
One of the trickiest things about any seder -- especially a large one -- is having the food hot and ready at the right time. I use my oven timers and chaffing dishes. With a huge crowd, I also highly recommend using disposable plates and cutlery. Depending on your level of kashrut, you can ask your guests to help out by bringing desserts, salads, etc.
For additional ideas, check out your local synagogues. Many of them will probably have some kind of seder preparation program. I noticed that Midbar Kodesh in Henderson is having a class on Sunday, March 10.
Most of all -- don't panic, enjoy! It's not a performance -- it's a service.