Re: First boat and kids want to wake board
We started our kids younger and this year our 5 year old will make the transition for skiing to wakeboarding.
As noted, you don't have to go very fast when they're starting. When they're young and light it doesn't take much at all to get them up. If you keep it slow the falls don't hurt as much. Getting up comes down to technique. I find beginners tend to want to pull themselves out of the water which tends to lead to a face plant. If you search youtube there are plenty examples of how to get out of the water. Here's one -
http://www.youtube.com/watch?v=I9qWJu0Vrpw&feature=related. The video excerpt is from a video series called The Book. It's worthwhile to get as it goes through everything from getting started to more advanced tricks. Once they're up they'll also want to make sure they have a proper posture (leaning back rather than forward). Note that the arms of the person remain straight when they're getting up and it's the legs that are used to push the person up after the board is starting to plane on top of the water.
You'll also need to determine if they're regular or goofy foot (i.e. which foot will go forward). You can use this method if they don't already know:
"Stand "at ease", arms at your side, and have someone push you from behind right in the middle of your back. If you put your right foot out first you're goofy. Left foot you're regular."
In terms of getting a board, the size is determined by their weight. Here's a chart you can use -
http://www.evo.com/how-to-choose-a-wakeboard-and-wakeboard-size-chart.aspx. You might be able to get a board/binding set that can be used for both of them. For a rope, you'll want to avoid using a ski rope (those stretch vs a wakeboard rope that doesn't). It won't matter so much for just learning, but once they start looking at getting some air, you don't want a rope that is springy like a ski rope.