Streets & Trips 2010 will do a better job of what you want than 2007 would have. I believe all of your pushpin questions will be well-answered by 2010.
However, you still may be challenged to achieve your last objective of incorporating multiple routes on a single map, subject to my suggestions below. While you can import route data files, S&T will still only compute one route at a time. Therefore, it is not straightforward to combine multiple routes on a single map. On this forum, there has been as least one request to add this feature to future editions.
You may be able to work around this somewhat, nonetheless. For instance, you could use color-coding of your pushpins (or different shapes)for your various bus routes. You could compute routes separately (with the data you want) and then use the line-drawing feature to 'connect the dots' following the computed routes. Then export this information as a GPX file for each separate route. When you have done this for all your routes, you can re-import all of these GPX files into a single map file for printing of the master map.
Impertinent Question: Isn't it a bit late to be planning school bus routes or are you looking ahead to 2010?