We are a family of five and have taken the Autotrain several times over the past six years. As mentioned before, for a family of a certain size and who live close enough to Lorton, it's cheaper than flying and having to arrange for ground transportation. Given last October's gas prices, it was even cheaper than driving. Last year, the cost for the five of us (in coach) and our mini-van (check your minivan's dimensions, you might qualify as a regular sized vehicle, our Sienna does) was $594.00. I booked the tickets in May for our September trip and we were able to take advantage of the kids-ride-free program. I'm guessing it's not when you travel but when you book that matters.
We find the Auto Train the most hassle-free and comfortable way to travel to Florida. Our children have always enjoyed the experience, even when they were very little. Our daughter was a toddler the first time we traveled by train. If you can enjoy travel with a toddler, that's saying something. We don't have any electronic hand-held games or personal dvd players, but we bring books, cards and games (a small round serving tray is great keeping dice from rolling off a table). Usually, we wind up making friends with other families who want to play too. It really passes the time quickly.
Sleeping on the train isn't so bad even if you don't rent a sleeper. We've done both. I can't say I slept better in the narrow berth than in the reclining seat in coach. When the kids were really little, we booked two sleepers, one in which the two youngest shared the lower berth and I would sleep in the upper berth. The other, dh and oldest ds would use. Now that all the kids are old enough to sleep in coach, we do just fine there. The seats are wide and recline. I think I remember pillows and blankets onboard but we bring our own pillow and little blankets. I also bring ear plugs and my eye shade. So far, we've never arrived in Florida feeling tired or fatigued like we do the times we've driven or keyed-up and weary from the airport experience the times we flew. We get off the train feeling like our vacation began the minute we set foot on the train.
As for the food, maybe we don't have refined palettes, but we thought the dinner was pretty good. By the way, coach passengers have the same menu as those in other categories. We've eaten steak, salmon, lasagna, and chicken as coach passengers. Maybe the difference was the complementary wine with dinner. I don't remember if that was offered when we booked coach.
If you haven't already, check out the transportation board for posts about the Auto Train. People have posted a lot of good advice about how to make your kids and yourself most comfortable on the train, pictures and accounts of their trips on the Auto Train.
P.S. We found out the hard way that tickets are refunded up to the time of travel. With several hours to kill between getting off the ship and boarding the train, we decided to go to the movies and have lunch in Orlando. We underestimated how long it would take to get to Sanford from that part of Orlando and wound up missing the check in deadline by fifteen minutes.

I didn't expect a refund would be granted and was surprised when the agent, almost in the same breath in which she informed me that we were too late to check in, told me the tickets would be refunded. It took a few days to show up on my credit card, but all the money was refunded.