What zoning ordinances would discourage retirees from a neighborhood?

I live in a town that is *heavily* skewed toward retirement age folks — more than 65 percent of the population — though there aren’t any official “retirement communities” in the town. There is currently a problem with getting younger workers in to care for them, such as doctors, nurses, care workers, etc, and those who do the physical work around town, from grocery store stockers to plumbers, utility workers, etc. There are lots of jobs available, many of them pay very well, but they’re having difficulty recruiting quality workers because there are few homes available for these younger people with families. Many of the homes which are available are so because their previous retiree owners died or had to move to places with better access to medical care, and the homes were built or converted to accommodate disabled or elderly folks. They are one or two bedroom (with one a den with no closet), single-story with small or no yards, are built to be accessible, and are not attractive to families with children, or who might want to have children. New retirees love them, though, since the homes are already ready for their own declining years, and they’re generally snatched up quickly by these new elder residents.

So far the addition of three new neighborhoods have just resulted in retirees buying them up too, and further putting a strain on the already limited human resources in town.

The planning commission and city council (made up mostly of retirees!) are considering zoning ordinances for the newest neighborhood that would attract families and younger purchasers, but discourage retirees from being interested in these new homes.

They already have the funding to build a brand-new K-8 school to replace an old school that is now in the middle of an almost all-retiree neighborhood. The school will be built in what is now empty land, and will be surrounded by a new-built “family neighborhood” with a huge new playground, and a pool with a water-park style slide and other youth activities, to attract the workers they need — but the community, including the elderly who already live here — are concerned that those new homes will also be snapped up by additional retirees instead of the young professionals that are desperately needed here.

This is a wide-open urban-rural interface area with lots of natural resources, near a national park, with hiking and even skiing opportunities for young, active people.

The city is looking for ideas for zoning ordinances for this new neighborhood. So far they are considering no parking of RVs in yards, no oversize garages, requiring large lot sizes, grass areas, and banning xeriscaping or rock yards (in the Pacific Northwest, where water *really* isn't an issue, unless there's too much of it).

What kind of zoning ordinances do you thing would discourage retirees from purchasing these homes, but would discourage their interest in purchasing homes in this neighborhood, and making them more open for the families they want to attract?
We are in a fairly rural area - about 2 hours from the nearest real "city," and about 90 minutes from the nearest mall. It has a sweet, historic downtown that is actually pretty healthy, compared to most downtowns these days. There isn't much nightlife. Just a multiplex theater, an older theater, bars, and, frankly, "old people" entertainment - artsy type events.

There is decent retention of area high school graduates after college, and excellent retention of vocational types. The school district has a really strong science program, surprisingly so for a smaller town, and a better than average community college. There is also a strong sense of community among the non-retirees. A lot of them have been here for generations, but they do accept new people pretty easily.

Housing prices are fairly low, for the region, I'm looking at an 8 acre lot just outside of town for $88K, and plan to build on it. Houses are usually under $200K. But then I grew up in Calif