the hyatt is the 'pick' of resorts. However you won't get 50% off a second room unless it is occupied by 2 children under 12. As soon as you put an adult in the room they charge full price for the two rooms.
However this is such a great hotel with a lovely kids club for young children. With 7 of you you would have to have 3 rooms as they only allow a maximum of 3 ppl per room. This would put the hyatt over your budget.
The mercure is another large resort and they have cheaper rooms. The price does go up if you want breakfast included. They have a small kids club and a free shuttle bus to the hardy's sanur. There are plenty of shops and restaurants around this area.
Besakih is a great budget beach front hotel, older rooms, but a lovely beach front area and a nice pool overlooking the beach. Other beach front properties would be inna sindhu, larger, wide beach frontage, respati, also beach front. Peneeda view is also beach front next door to the hyatt, the beach front is not as nice but is it very central. The hotel is relaxed, rather laid back, 3 pools and they have some 2 bedroom family rooms. IF you like this place it is cheaper by booking with online agents.
You could also look at puri santrian, it is a larger hotel, big beach front down near the mercure.
I am glad you changed your mind about the plaza suites, it would have been difficult to get all the kids and family loaded into the shuttle a couple of times a day. With a beach front hotel you are only steps from your room to give the kids a sleep etc.