Tree bags are great! I'm so glad to see them being used - I'm sure that they save many newly-planted street trees from an early demise.
Plant in early fall, if possible, once the weather cools off, and I'd suggest considering a zelkova. It has a shape somewhat like the elms you miss, and my understanding is that it's pretty tough. It's also a nice "unmessy" tree, with some fall and winter interest.

I believe there are newer cultivars of elms that are resistant to dutch elm disease. Have you tried the tree forum ?

Kathy

Thanks for the responses. I've been a little wary about elms. Clearly, we've got a serious infestation of the disease in our yard (last year we lost another beauty to it). I question whether resistance will last the life of a tree. Those pests mutate pretty quickly. I know that the NPS has enough confidence to be planting the new varieties, but knowing how long resistance usually lasts has given me doubts...