OK Apple - You've had a blood rush to the head seeing that Epic v10. It makes sense - it is an incredibly sexy piece of kit. But we need to pull you back to earth a little (though not too much!!).
If you want to go long and fast with a view possibly to racing, the Epic v10 is the beast for you...but you will hate it. Speed depends on two things - length and width. Long and narrow. 6m boats are faster than 3m boats. The Epic is about 6m long and 48cm wide. That equals long and narrow which equals fast.
I've been paddling for several years off and on. I've been paddling as a minimum 4 times a week since March. My last boat was 68cm wide and I thought it was stable. My Spirit PRS is 50cm wide (and just under 6m long) and it is pretty unstable. I've been on it 20 odd times and I'm ok on flat water, but the minute I get a boat wake or any side waves, I'm so close to going over. I've had lessons and, although I didn't fall out, I'm not yet leaning it over as far as I should and my brace strokes need work. When I bought the PRS, I was just at the edge of being able to handle it. Practice makes perfect and I am one stubborn girlie

I wanted something to extend me and allow me to push my limits. This has done this...and how.
So...you will need to find the equivalent of the HT MTB.
I prefer sit on kayaks or skis. It enables me to move my legs around a bit more. It I fall off, I jump back on and the self draining hull deals with the water. Mr Moo prefers enclosed or sit in kayaks - if he falls out, he swims his yak to shore, empties it out, then gets back in. Time waster. True kayakers (the crazy sit in guys) are a strange bunch and they wouldn't have it any other way

You may prefer the feel of a sit in (I won't hold it against you!!). If you search for photos of a Finn Endorphin and a Finn Multisport - these have the same hull exactly but one is sit on and the other is sit in. This is great to see the difference.
You'll need to look at sit on kayaks/skis around the 3-4m mark. Nothing less than 60cm wide. You may even be looking at something around the 80cm wide mark. It seems huge, but is stable and will enable everyone (you and the kids) to learn on it. And the dog to sit on it

If possible, try to get some lessons. It isn't just a case of paddling - the better your technique, the less effort you will be putting into your stroke. Faster with less effort basically. Also, there are different strokes - power to go forward and backward, sweep for turning, high and low brace for stopping yourself capsizing. There are others but these are the major ones.
It doesn't matter which kayak you get - the basics are all the same. I bought a book by Terry Bolland with all the basics outlined. He just happens to be the owner of my local store and the most experienced paddler you could meet. I'm not sure if his book is available else where but look for it if you can as it is an invaluable resource. It also describes all the boat types, paddle types, strokes, how to read the river etc.
OMGosh I've gone on and on and on!! I'll stop now before my fingers fall off

Take this info to a canoe/kayak shop and let us know how you go. Can't wait to hear.