When you refer to taking the Turnpike down to the Miami area and picking up US-1, do you mean you plan to take the original Turnpike down to where it ends near Miami Gardens and then connect to US-1 in that area (perhaps by taking I-95 to US-1), passing near downtown and through Coral Gables, or do you plan to connect to the Homestead Extension and follow that down to US-1 where the Homestead Extension ends? The latter is by far the better option to avoid loads of traffic lights, etc. There is construction on the Homestead Extension, however.
To piggyback on Max Rockatansky's comment about US-27, let me offer you a different route to use between the Keys and US-27 on the way back: When you come north back out of the Keys, before you reach the Homestead Extension, make a left onto Krome Avenue–the left turn is almost immediately after Card Sound Road merges from the right and there's a little green sign for "Homestead Downtown" in the median as well as a Race Trac station on the far left. Follow Krome Avenue north for 37 miles and then make a left onto northbound US-27. You'll bypass the Miami metro area to the west and you'll avoid the highway construction and the toll. Some people have occasionally expressed safety concerns about Krome Avenue, but I've never had an issue.
Also, on your way south, if you are not motivated by clinches, you can bypass the worst of the Turnpike congestion by taking Exit 71 for FL-869 (the Sawgrass Expressway) and following that south to I-75, continuing south on I-75 towards Miami, and then taking Exit 5 for the Turnpike towards Homestead. The Sawgrass is not exactly a lightly-travelled road either, but it usually moves pretty well.