I think using hoses and sprinkler heads is too much work, and hard to do
accurately, so I would suggest an irrigation system.

For delicate areas, I would install a drip irrigation zone, which can
deliver water to the roots without disturbing the foliage.

For the lawn area, your choice is either multiple pop-up heads (they
spray in a circle, but can be adjusted to a wedge shape, or pop-up
impact heads (which can also be adjusted to a wedge shape). Generally,
the impact heads have a further throw, but are also more subject to
wind, so you might prefer six or eight pop-up sprayers to one or two
pop-up impact heads.

I suggest you do need a timer, as most controllers function as timers,
and also can control volume. It is a better practice to water early in
the morning, as you lose less water to evaporation, but the water is not
lying on the flora all night, which can tempt diseases.

Unless you are strong and handy, having a system installed (they also do
the designing and checking pressures, etc.) is not a bad idea. I had my
back yard done professionally, then brazenly stole their techniques to
do my front yard and flower beds myself. The installer even suggested
this, and put in a couple of extra control valves when he built the
manifold, saying I would probably need them later.

If you want to self-install, you will have to be prepared to do a lot of
trenching and dealing with underground utilities, but I think most
manufacturers offer a design service, and my experience is that
irrigation supply houses do too (although a lot of them prefer to deal
with installers, rather than homeowners). The big box stores seem to me
to offer inferior parts, incomplete inventory, and no design help at all.

Spending some time at the web sites of some manufacturers should help
you understand what is available, and how to plan your system. One good
recommendation is that you arrange it so that every area is covered by
two heads, which reduces the chance that you will have any gaps in coverage.

Kiran wrote:
There was some discussion of sprinkler here. I am a newbie too and
would appreciate all advice about my specific situation:

1. Two 30' x 60' backyard TRIANGULAR lawns (flowers along the long
edge). There's a walkway along the diagonal edge which needs to be
avoided.

(This is a 30 x 60 rectangular lawn in which the previous owners put a
diagonal walkway in the middle.)

2. Two 12' x 15' rectangular front gardens (no grass, only flowers and
plants, many delicate), with a walkway in the middle which need to be
avoided.

(Again, a 12 x 30 front yard with a walkway in the middle.)

3. Two 8' x 16' city parkway lawns, which can be watered together as
one 8' x 32', but there is a sidewalk along the long edge that needs to
be avoided.

As you can see, we need control over where the water goes, and also
over how powerful the spray is (due to flowers).

I am open to buying one or more sprinlers. When possible, I would
prefer flow control as well as metal construction. I don't need timer.

I am quite confused about various types (oscillating, impact, turrets,
etc) and would like advice on best types for our situation, with
specific brand/model recommendations if possible.

(Would like to avoid spikes because of 2-year old kids and also impact
type IF the jet would be too strong for them. They tend to run towards
any water.)