Ok, I can help you.
St. Augustine is about 30 miles from Daytona on I95. From Daytona to WDW is about 45 miles on I4. So, it's an all highway trip.
There is some construction on I95 between St. Augustine and Daytona and there is construction on I4 between Deland and Deltona. There is also construction on I4 after Downtown Orlando near the John Young Parkway.
Actual travel time will vary depending on traffic, etc. but it should take you between an hour and a half to 2 hours in actual drive time.
If you are planning on going thru Orlando at the "rush hour" times, consider using SR417. It starts in Sanford at I4/SR46 and ends at I4/SR192. It will cost you about $6 in tolls, but can be a huge timesaver.