What you do with the money after the sale has no affect on the tax treatment of the sale itself.
You don't qualify for the capital gains exclusion unless you also sell your home within 2 years of subdividing and selling the exempted land.
Assuming you remain in your home, you must deal with the capital gains on the land portion of the sale. You will have to determine the cost basis of the subdivided portion, I can't point to a specific formula how to do that. It could be as simple as so many dollars per acre, but it might be more complicated in your case since the land you are selling is restricted use. (In other words, suppose you bought 10 acres zoned as residential/farming for $100,000. It might be reasonable that the cost was $10,000 per acre since all the land is basically the same. But if 3 acres are restricted use, and can't be used for a home or farm, then it might be more reasonable that the restricted land was $5000 per acre and the usable land was $12,142 per acre.) You may need the assistance of a real estate appraiser.
Then, you must also adjust the cost basis of the remaining property for whenever you get ready to sell it. Suppose you bought the entire property for $250,000 (your cost basis), and you determine that the cost basis of the portion you sold was $10,000. You sell for $25,000 and report a $15,000 capital gain. You would also reduce the cost basis of the remaining property by $10,000.
