The regular DS is a bit heavier (not much) and not as easy to find since the DS lite came out. My daughter got hers when she was 5 or 6 (she's 9 now.) She got me the DS lite for this past Christmas. (I have trained her well, lol.) The DS lite is lighter weight, brighter screens, and holds the stylus MUCH better than the original DS. A huge vote here for the DS lite.
That said, the newest of the new DSi is now out, just came out a month or so ago. The DSi also has a built in camera, and you can edit your photos, use fun effects on them, etc. You can also access games from the Nintendo Channel to your DSi if you have a Wii. One thing that DSi does NOT have, that the DS and DS lite do, is the slot that allows you to play older Game Boy Advance games.
I am an old-school gamer, started with ATARI. (man I am OLD.) My daughter started playing when she was 1.5 and she kept taking the controllers out of my hand. So our game favorites may be beyond someone just starting out in the Nintendo world. However, I'll give a few that I think might be good for her. Let's see, Nintendogs is a lot of fun, you have puppies you take care of, walk, get accessories for, etc. Cooking Mama is great, you make different recipes, heck I even like this one. I would also suggest a classic....Super Mario Brothers. It really introduces someone to the basic platformer game, and while it does get harder as the levels go up, your husband would also have a bunch of fun teaching her how to do it.
There are TONS and I mean TONS of older Game Boy Advance games that can be played in the DS and DS lite. Several are on par with games your daughter may have played on Leapster, or are a good progression from Leapster to the Nintendo systems. You can find Game Boy Advance games VERY inexpensive used at GameStop stores. The reason I am saying this, is that's a good way to get a bunch to get her started, to see what kind of games she prefers.
We play all kinds of games, and in addition to our DS handhelds, we have Playstations, Xbox 360, Wii. I try not to ever count how many games, because then I think about how much money I've sunk into it all and I feel queasy. BUT, the reason I am saying this is....my favorite game, absolute favorite, and one of my daughter's favorites...is Animal Crossing. We have it for GameCube, Wii, and we each have one for our DS. You live in a town, have animals for neighbors, earn money by fishing or digging up fossils, fix up your house, etc. It's an ever-changing game with new neighbors, seasons, events for different times of the year, etc. It's an absolute BLAST and I would highly suggest getting this game. Since my daughter and I both have them for our systems, we can go into each other's town, too. The one for the DS is called Animal Crossing Wild World.
You really can't go wrong with a DS of any kind. There are games for everyone. One thing that makes us mad about some games is when they say they are "geared for girls" or something, like a GIRL can't play "regular" games? Or they have to be easy and fluffy? (Obviously I take offense at this being a gamer from the start.) My daughter has had a subscription to Nintendo Power magazine for a few years, and BOY does she get mad when she sees stuff like that. She's beat about 95% of the games she has, and that includes Legend of Zelda Twilight Princess. She still will enjoy playing things that are lighter as well. And now I am officially rambling.
ANYWAY, there are plenty of DISNEY games too, so that would be a lot of fun for the trip.
