The Getaway is a great boat to start on, and for a family. I started with the Hobie 17 when my kids were young, did not know I was buying a solo racer. We outgrew it pretty quickly. When I soloed it though, what a rocket! The Getaway is tamer and easier to sail. That said, it does have some sailing chops. I was sailing with a couple of friends on their H16s on a big lake in some big wind, and we were all doing about 20 MPH together. But the room the Getaway has is amazing, you can pile on a ton of people and kids and still sail well. The Getaway also has easier and simpler rigging than the racer Hobies.
$5500 seems a tad high to me, unless the sails and tramps are newer than the original hull, or they are in really great condition. Especially this time of year, sailboats aren't exactly moving this late in the season. I'd try to negotiate it down some. Where do you live? There might be a closer boat. Where is the boat at? Maybe someone on the forum lives close to it who could take a look at it.
For learning to sail a cat, and especially for a family boat, the Getaway is a great choice. It's stable, hard to capsize, lots of room for the kids. My friend with a H16 sailed my Getaway for the first time a few weeks ago, and he loves it, so that speaks well of it's sailing ability. He was especially taken with the easy helm balance, the lack of weather helm in 25 MPH winds.
Here's a link to instructions to build a motor mount. I had bought the Cheata mount for my Getaway, but replaced it with this one. It's a heck of a lot cheaper and a heck of a lot better than the Cheata mount.
https://www.hobie.com/forums/viewtopic. ... otor+mount