You can absolutely take an alternative route while returning back. We have another package that includes Gosainkunda lake, where the trail diverts after Lama Hotel to Syabru Gaon instead of Syabru Besi. If you have more time, you can even do Langtang Circuit Trek, where you return back by hiking down to Helambu and finally to Sundarijal, entering Shivapuri National Park.