1. There are many shrubs and perennials that would work along the driveway.  I would look for something heat tolerant.  Ideally we would leave more space for shrubs, 3' is tight.  Why I mentioned perennials or ornamental grasses like a feather reed would work.  This list is for trees and shrubs. https://extension.colostate.edu/topic-areas/yard-garden/xeriscaping-trees-and-shrubs-7-229/  I would check out the local nurseries as well.  At this time of year, you want plants that were overwintered.  We have a month and a half of possible frost.

2. We do NOT recommend planting any ash.  Due to drought we have epidemic of ash bark beetle, and there is a new insect on the front range.  We tend to be too hot for ash.

There are tons on trees that are more drought tolerant that work in our area.  First, try to match the tree to your soil.  If you haven't done a soil test, I would do one now.  CSU is about a month out.  Another option would be Ward labs.  Let me know if you need more info on that.  

You might want to consider a smaller tree with the space you have.  I would plant the tree high since you are putting them in lawn areas.  Trees and lawns have different watering requirements.  Trees prefer less frequent deeper water (10-30 day cycle once established and depending on species) and need to let their bases dry out so keep a ring of bare soil around it.  https://extension.colostate.edu/topic-areas/yard-garden/small-deciduous-trees-7-418/  of this list avoid Aspen, purple robe locust and Euonymous.  

Here are the steps to properly plant a tree. https://static.colostate.edu/client-files/csfs/pdfs/TreePlanting_636.pdf

And lawn care- the more drought tolerant you can manage your grass and proper maintenance like keeping the grass at 3" to keep weeds down, will help the tree.  Be very careful with herbicides, as a broadleaf killer thinks a tree is a weed.  https://extension.colostate.edu/docs/pubs/garden/07202.pdf

Susan C.  TRA Horticulture agent

That is all great information thank you. What are some trees you think would do well for us? We want something with more "traditional" leafs nothing with falling seeds or branches, and something like looks good in the fall. Also have you heard about burying a pipe next to the tree so you water down and make the roots grow down?

We have no research on the pipe in the ground, more of a homeowner hack.  Roots are in the top 12-18".  Will root out eventually at least twice as tall as the tree so good to do a deeper watering now and then.  https://cmg.extension.colostate.edu/Gardennotes/635.pdf

All trees are going to produce some kind of liter, even evergreens. Golden Raintree is nice as the seed pods disintegrate.  Most of the crabapples now a days have persistent fruit, which mean they dry up and shrivel on the plant instead of dropping. Ask the local nursery for varieties with persistent fruit and that are fire blight resistant.  Canada Chokecherry is nice, it has fruit but the birds eat it.  There is a new variety called sucker punch because it does not produce root suckers.