A:Groups of high school seniors are usually as welcome as rats at upscale restaurants; still, I can recommend a few places without hesitation. The Rialto Cafe (934 16th Street, 303-893-2233), a snazzy, two-story eatery in the building that long ago housed the Rialto Theater, not only serves impressive desserts big towers of chocolate, huge portions, innovative designs but also welcomes dessert-only diners, even teenaged ones. I once brought a group of Westword co-workers there in search of late-night desserts to review for the Best of Denver issue, and if the managers let us in, theyll let anybody in. (The Rialto won the award that year, by the way.) Another option would be janleone (1509 Marion Street, 303-863-8433), a charming restaurant located in an old mansion off of Colfax Avenue; owner Jan Leones daughter makes fabulous desserts. And if the Snowball runs late, your best bet might be the noisy, see-and-be-seen Radex (100 East Ninth Avenue, 303-861-7999), which serves excellent desserts until 1 a.m. daily.