You may consider take a flight from Xiamen to Shanghai for a 3-day's visit and then take a train to Hangzhou of Zhejiang Province for another 3 days. Finally, you could take a flight from Hangzhou to Xiamen easily.

If you would like to rent a van and a guide for every place, why don't you participate in a tour group. Since you already have 8 people together, which could make up of a small group by yourselves. This method will ease your trip a lot~