MoJa've is nice... although getting on and off the water at Katherines can be a nightmare. 

Havasu E is great, just don't double dose you'll be frying eggs off your brain. ..   If your going with kids I would lean towards the southern end by Sand Point.  You can launch at Cattail/Sand Point and go from there to avoid the madness at Site 6 or Windsor.  Less crowds and plenty of coves to day camp in.