I made some calls on this matter, Irfan, and e-mailed you a contact who likely can help you secure tents and sleeping bags at a good price. What you need are family-sized tents with as much solid-wall material as possiblenot tents with a lot of mesh. Good examples would be Eureka!'s Equinox 6 (sleeps six$300; www.eurekacamping.com) or Coleman's Weathermaster 3-Room Tent (also sleeps six$200; www.coleman.com).
Sleeping bags are going to get awfully expensive when it comes to supplying enough for large groups of people. Even the most inexpensive synthetic-fill sleeping bags are going to cost between $50 and $100 each (Coleman's North Rim bag, rated to zero degrees, is about the most reasonable at $55). Here I'd be inclined to purchase large quantities of good-quality fleece blankets, which can also cost around $50-$60 but are generally more flexible than sleeping bags and, to put a fine point on it, can cover more people at once. Do some Googling for "fleece blankets" and you'll find some good deals.
For other readers, you too can lend a hand by offering cash donations to one of several organizations active in Pakistan (and yes, I know we have plenty of problems in the U.S. with KatrinaRita victims, so try to help them as well). Check in with these websites: