Not much street food to speak of in Santa Fe, although the south side of town has quite a few good taco trucks and a number of "gourmet" food trucks have sprouted up in recent years. If he's still around, Roque's carnitas cart on the Plaza does delicious steak tacos that are more like a fajita than what non-New Mexicans think of as carnitas, but I have no specific "street food" recommendations otherwise. Santa Fe has quite a few vegetarian/vegan restaurants and should have a few celiac-friendly spots, though perhaps less so if you're interested in trying traditional New Mexican food. The local weekly arts and entertainment paper,
the Santa Fe Reporter, has good food coverage and is probably the best way to get your culinary bearings. Check out
Edible Santa Fe, too. Many other dining guides are of course available online.
As far as ruins go, your best bets are
Bandelier National Monument,
Puye Cliff Dwellings, and
Pecos National Historical Park. Bandelier is quite large, but the most accessible and kid-friendly section consists of a large pueblo ruin and a number of cliff dwellings located at the bottom of a scenic canyon. A paved, fairly easy loop trail runs to most of the major sites and there's a nice, recently remodeled 1930s-era visitors center too. In order to visit the park you will need to drive to the town of White Rock and then catch a (nice, clean, nearly brand-new) bus to the Visitor's Center.
Puye is another cliff dwelling/pueblo site. It's owned and operated by the Pueblo of Santa Clara, whose ancestors once lived there, and can be visited via guided tours led by Pueblo members. The tribe also demonstrates traditional dances for visitors, and you can buy Pueblo pottery and other arts & crafts in the vicinity. The site is closed for traditional ceremonies at certain times of the year.
Finally, Pecos National Historical Park preserves the ruins of what was one of the largest and most powerful Pueblo villages at the time the Spanish arrived in the 16th century. You can tour the large (unexcavated) hilltop pueblo ruin and the excavated remains of an extensive mission complex built by Spanish priests (and Pueblo laborers) during the first half of the 17th century. It gets a lot fewer visitors than Bandelier does, but is a neat site with a lot of history. It's probably a half-hour or so east of Santa Fe, right off I-25.
Oh, and since you'll have little ones with you you'll definitely want to make sure you check out the
Museum of International Folk Art on Museum Hill and the
Meow Wolf interactive adventure/art space on the south side of town. Meow Wolf is a bit pricey, can get crowded, and isn't really what most people from out of town have in mind when they think of Santa Fe, but is totally cool for people of all ages and your kids will love it.