Denison texas
 

I am looking to take my family on a road trip from denison texas to key west. Going to take 3 days to get there then stay in florida for 5 days. What are some places to do or see on the way?

Can't see that you'll have much/any time for sightseeing en route. That is a full three day's drive by the most direct route without any stops other than meals/fuel/sleep. At least 8 hours per day butts in seats. Likely closer to 10 hours/day if you run into construction and/or traffic.

If you did have time to sightsee (which I agree you really don't), you could go via Lafayette, La, New Orleans, the Florida panhandle, Orlando and Miami. There's stuff to see and do in all those places.