Necessary to acclimate plants?

Is it necessary to strengthen my plants and acclimate them to outdoor before transplanting?

I am about to germinate seeds in a wet towel, haven't yet decided what soil to use (suggestions appreciated), and going to leave plant in a greenhouse style room that's surrounded with windows. The room gets hot and faces south for extra light.

At some point, I want to transplant them to an outdoor sight. At what size are they most resistant to transplant shock and do they need to acclimated to the outdoors before I put them out? Once they're big enough to put outside I'm just going to put them in my vegetable garden next to my tomatoes and eggplant, is that cool or a big no-no?

All your help is much appreciated.

Notice how people always seem to get sick when the weather changes quickly from one season to the next? While most people do not lay down and die, their condition keeps them from optimum health. Same is true for your plants, you can most likely put them right outside in one go, but they will almost certainly pay for it. Introduce them slowly to the outside by putting them out for a couple hours a day, gradually increasing their exposure. This should not be to hard for you to do if you are planning on putting them in your yard. (Hopefully you are in a really remote residence or have some other way of keeping the girls private.

As far as mix, all I have used so far is a creation called "moonshine mix" -- look it up, its basically a mix of several ocean forest products and a bunch of vermiculite. No fertilizers are needed for the first 2-3 weeks at least when using it, and it starts the seedlings off quickly

Thanks, I appreciate it.