In what order are the attributes of the entity in your domain model? Try putting them in the desired order. You might need to recreate the mapping...
There's no explicit way to set the ordering but that might influence it. I'm not near the source code now so I can't check.
I haven't tried this myself but I think it should work:
In your Domain-to-XML mapping, child elements are retrieved over association by default. However, you can specify a microflow to retrieve child elements. In your microflow: