It's the amount of paint that is applied, rather than the method of application that is important for durability. Painters often paint to cover, rather than painting per the manufacturers specifications.

Usually two coats will give the best result.

Sheen (gloss, eggshell, matte etc) will also make a difference, with higher sheen paints being easier to clean.

Rolling usually gives the best look, and if spraying, the paint should be back rolled.

Due to kids I think semi-gloss would be a happy medium. Good washable, but not super shiny. Yes, 2 coats. Don't try to glob the paint on to cover in one coat.

The higher the gloss level, the more any and all wall imperfections will show. With kids, I would use the "eggshell" finish. Very scrubbable, and easy to touch up. Quality of paint is also a factor. My favorite for walls is California Ultra Ceramic. Also comes in a matte finish.

Yea, spraying or rolling has nothing to do with the chalkiness. If the paint is chalky that just means that the paint is cheap flat paint. This type of paint has no washability. Also, the paint should always be rolled, even if you spray. This is called backrolling and is done to even out the paint finish as it is very difficult to spray a wall perfectly and also the stipple left behind from the roller makes touching up possible. A sprayed wall can not really be touched up. Semi gloss is too shiny for wall painting, though we may see that in a small bathroom or on trim. Go with the eggshell.

eggshell at most, semi gloss is way to shiny

First off I do all the painting and have been for too many years. Hubby hate to paint. I use satin on my walls. My kids are all grown and I still use it. I only had 2 children so there was average abuse to the walls. Used eggshell once when my children were young and it didn't hold up and it did have a cheap look to it like flat paint. Flat paint is the cheapest paint you can buy and looks it, then eggshell is next to cheapest. I recommended semi-gloss due to its durability if you have a lot of kids. Yes it has more of a sheen, but if you have a lot of kids to take care of, who is looking at the sheen on the walls. With kids I wouldn't recommended anything less than satin. Take it from a mom who son drew on his bedroom walls with an ink pen 2 days before putting on the market. 4. Semi-gloss

Semi-gloss paint finishes are known for both their durability and washability. The paint, with its medium sheen, is well-suited to moderate and high-traffic locations. Easy to wash, the paint is used on woodwork and trims and is often used for covering the walls of a children’s bedroom or playroom as well as the walls in the kitchen or bath.

I'll be a minority with functionthelook: Semi-gloss. I've got little kids and their dirty hands are attracted to wall surfaces. I personally dislike low-sheen paints. Eggshell and lower on a kid's wall will keep your painters busy every year.

Spend more money on drywall finish and the classic, "flat/matte paints will 'hide' imperfections" goes away.

There's no disagreement that for a given paint line, semigloss/satin is more cleanable than matte/flat. Why would you settle for a less cleanable option? Besides, satin/semi-gloss is actually not that "shinny." Shinny to me is a French polished guitar :-)

I vote a good quality eggshell -- cleans up just fine. To me, semi-gloss walls belong in schools and hospitals. Not quite the look I'd want in my home. But, hey, everyone's needs and wants are different.

If you are trying to picture in your mind how semi gloss would look at your walls....think hospital! Everyone has a different "style" of decorating, but the reflection of light from semi-gloss walls would be very unflattering.

hatetoshop - you beat me to it!

They are children, not wild animals! Unless they are so rambunctious that you need to protect everything in the house with plastic sheeting, eggshell on the walls will suffice and your home won't look like a fast food restaurant.

Go to Lowes or Home Depot and pick up some of the little testers they sell. They come in different sheens and try them out on the wall. See which one you like.