Good morning! I have my two favorite shade tree recommendations below.

Catalpa: These are fast growing trees with large leaves and white flowers in the later spring/summer (May - June). In the fall they have long seed pods. I like these because they are fast growing! Potentially reseeds but I have not had an issue with them. Will need some regular watering and should be readily available at majority of nurseries. 

Kentucky Coffeetree - These are a great trees for the Front Range! They can look a little sad when they are younger but are great stable trees. They have white flowers in the summer and then bean pods in the summer. If you do not want the seed pods there is a sterile variety called espresso! Kentucky Coffee tree does well in all the harsh conditions of Colorado :)

Hopefully this helps and thank you for reaching out!

Rachel

Yea no worries! You can do the Kentucky Coffee Tree espresso - that one is seedless so non-toxic to dogs!

The other one I would suggest is a golden raintree! Another one with seedpods - I seem to be bias towards them. An oak is another suggestion - I would suggest the bur oak. This do very well here and are tolerant of all soil types!

Hopefully one of those work!