Dear Mohansir,
If you are planning from Chennai , it will be convenient. You have plenty of budgeted hotels in and around Mangalore. If you are visiting only Mangalore max 2/3 days will be sufficient. While u are in Mangalore you can visiti Dharmastala, Katil, Manjunath and Subramanya temple. Mangalore sea coast is also worth visiting if you are children accompanying. Food is not a problem. Nov/Dec will be ideal . You can as well plan Sringeri/Udipi/Mookambika by engaging a vehicle to/fro from Mangalore. Happy Journey. Rgds Krishnan