Hi Daniel,
From my own expeience it couldn't have been more "soft sell". There was none of the "special price/discount if you sign now BS that goes on at regular timeshare sales pitches. There was ONE story of a DVC salesperson being a bit pushy on the DVC board recently, but that's about the only time I've heard of that.
It is definately worth taking the sales talk and seeing the units, unless you take the time out you really won't appreciate what is on offer. You can book this at Disney, they have booths in the parks, hotels and Down Town Disney. There is a creche for the kids so it's a good idea to put them in there for an hour while you talk over the details with the sales staff, IMHO it's a waste of time to have the kids crawling over you when this is going on. The kids get bored and you get distracted, if you're thinking of handing over a chuck of money the last thing you need is to either lose the track of things or just plain want to get out cos the kids are driving you crazy.
Before doing that it's worth doing as much research as you can, unfortunately you won't have enough time for DVC to mail you a copy of the video and unless anyone in the UK has a copy ( all mine mysteriously have not returned

) you won't get the chance to see it before you go. Do ask them for a UK format copy to bring home with you.
IMHO, there are a couple of things you need to decide going in.
1)Would DVC be the only place you'd stay in Florida or do you like to move about a bit?
If you would ONLY want one base then DVC is likely to be a costly option, the more flexible you can be, the better value DVC can show you. I know some people don't want the hassle of checking out/into another resort while they are away. I can understand that view, but with the premium one pays to stay "on site", be that Disney or Universal , I find it hard to justify paying that premium if I'm offsite visiting other parks/attractions. As I pointed out on the other post, avoiding weekends can be a huge saving on the number of points you need. Plus with a little banking and borrowing you can manage your account to keep down your initial outlay. Now it's certainly possible that after a couple of years of using your points you may decide you need a few more ( many people do) , but I think with 3 kids already you are already at the peak (a 2 bedroom villa) of what's likely to be your requirements for the future.
2) The size of unit you'll need in the future.
DVC is a longterm investment, while now you will need a 2 bedroom place, in the future you may be able to get by with just a studio on some visits. Granted that will mean you could have the luxury of not worrying about staying elsewhere at weekends or pampering yourselves in a one bedroom, but you don't want to be in the position in the future where you feel you're wasting points just to use them up. The flexibility of the points is also great in that if, in the future, when your kids are grown you could get different units for you, wife and some/one of the kids and get one/two of the others a unit to share or one each with their then partners

. I know that's a frightening thought while they are still young, but trust me they grow up damn quick LOL. Again as time goes on it offers you the chance to bring your kids and their kids away for a big holiday (or maybe just the grandkids)
3) How often would you want to visit Florida ( or go somewhere else).
The most efficient use of your points is to stay at DVC resorts. The minimum you need to visit is once every three years, but you do need to be pretty organised to fit in to that time frame, coming from the UK is probably easier than people living in the US, but even so, it isn't simple. Really once every two years is probably the "regular" minimum and allowing an occassional 2 year break.
There are plenty of ways to use your points outside of WDW, but there is no guarantee those options will always be in place. IMHO it's probable, but they can't be guaranteed neither are they as cost effective as staying on one of the DVC resorts.
Finally you have the choice of SSR (from Disney) or buying a resale. SSR has another 12 years of "shelflife" , usually buying a resale would work out a lot cheaper in the short run.
If you give a brief outline of what you think you're going to want to do and how you usually vacation , i.e. staying in one hotel or moving around, it will help people to give an educated answer to your likely needs. In your situation I wouldn;t but points to cover all your needs for a stay at the moment, in the future your needs are likely to be less.
There are ways to work round your current needs by using DVC as a "highlight" in a vacation and staying either in a suite hotel, two rooms or probably the most cost effective answer a private villa. For example staying in a villa for the first 8-9 nights of a trip to do USF, SW, BG, shopping etc then finishing up on Disney in a 2 bedroom for 5 nights to cover the main theme parks.