dabac

Balance bikes.
Training wheels don't provide any important training.
Kids don't have the concentration/separation ability needed to use the training wheels only to keep them from toppling over. They'll ride them like big, fast trikes and not get any balance training done.
At best, they might pick up some braking skills. Any kid that's ridden a trike already knows how to pedal.
If you start them on balance bikes, once they're steady on them I've seen kids transition to pedal bikes in less than one hour, entirely without drama or abrasions.

The bike industry is very ****genous. Similar money buys you comparable products, regardless of brand.
I'm not too keen on 3-speeds. Ratios are too few and too far apart to let you keep your legs humming along nicely.
Also, I often find the ratios awkwardly placed, with the top gear not particularly useful. They can often be made nicer by fitting a bigger sprocket and keeping the lowest gear as a bailout gear. IMO 5-speeds and above makes for more harmonic riding.
I'd look for a mixte prior to Dutch/Townie. Dutch/Townies can be amazingly heavy, heavy enough to detract from the ride experience.

Chek out the local rules first. Sidewalk riding - for adults - is often prohibited.
And unless AZ is above average in friendliness, I can pretty much guarantee that even a parent riding sedately while shepherding the kids along will make some people angry.
If you think sidewalk riding is the option for your kids, follow them on inline skates or jogging instead.
There are tandems, trailers, tow bikes and brackets that lets you tow a regular kids' bike behind another bike.
There's the Surly Big Dummy, the Xtracycle conversion kit, a considerable number of cargo bikes.
A friend of mine went with the "road train" concept. A towbike hooked to his bike, then a trailer hooked to the towbike.