I laughed out loud at the "preschooler outing" you mentioned. Not sure what that was about...wasn't what I was expecting, I guess.
I think it does NOT depend on the age of the child but on the temperament of the child, and the um, PLANNING of the parent. For example "window shopping" (boring for a small child) at nap time, and then going in to tiny shops full of "lovely breakable things" isn't wisdom nor is it an "outing" that a preschooler would be interested in. "Be quiet, don't touch" is not fun. Not even a little bit.
I loved a phrase another mom used, so I'll quote her: the more you go out on fun things (for all of you, please) the better they will learn "the rules of engagement" and be just fine with them. SCHEDULING was my key to success. Joseph was 37 months old when Victor was born, and we've always gone out everywhere. But we always had a schedule: they get up at about the same time every morning, go to bed at the same time every evening, have naps at about the same time every day, and their meals and snacks were always about the same time. Once you have THAT schedule set, everything else is super easy, you just work your fun time around their biological clocks (schedules for necessities like sleeping and eating). Yes, some of it get changed a little until their old enough: the symphony changed to big band concerts in the gazebo downtown, or a concert/picnic in the park (if under the stars, then in their pjs with a snack and a blankey). Theater moved to Children's Theater. The mall: we just went earlier---like mall walker kind of early, and ended it with a carousel ride and some time in the little play area.
When my guys were very small, they did trips to the mall (with their fun included), small fry club, art museums (they especially liked the cowboy stuff and the Chinese art because of all the vibrant reds), to see music shows, street fairs, farmers markets, we'd go to the airport observation park to see the airplanes zoom in over our heads, and then hop on and off at different locations on the busses, riding trains, exploring the touristy stuff around us, my oldest was 3 the first time he rode a mechanical bull and a camel, they go to any kind of restaurant (they love ethnic food), movies, just whatever we saw that was around that looked interesting.
Now my guys are ages 5 and 2. This week they go to the park, a local playground, 2 kung fu practices, my shopping that needs to be done, get hair cuts, the farmer's market to explore and sample, storytime and a craft at the library, horseback riding lessons and playing on a local farm, a picnic and petting zoo, a friend's Tball game, the beach, church, an equestrian expo, and a polo match. Next week I'm really looking forward to taking them to the Tall Ships Competition to tour The Bounty and see some other awesome sailing ships. Hoping to go on an excursion on one of them, if we have time....that evening we leave to go to Disney World, hoping to beat the after school, summer vacationers. We can do ANYTHING as long as we keep them hydrated, interested, fed, and rested. We just plan our outings around their naps. They don't really snack anymore, but there's always something in the diaperbag just in case.