Last time we lived in Cargo Hostel which is near 東部華僑城, not expensive, RMB $390 for 6 people room. Buy 東部華僑城 ticket at their counter, RMB $210 for two days pass. You may consider. I booked the hotel from ctrip, pay at the counter.
Other moms suggested to book the hotel in Taobao, 全瀑布酒店都係300人仔, it is cheaper than 凌海.