there are a few places you could go to outside of flamingo land.
there is eden camp, which is a good 1/2 day out about 10 minutes away from flamingo land, tis a WW2 historical place, really good for the kids to visit, v interesting.
Pickering, you can take a steam train ride - about 15-20 minutes away - loverly quaint village too.
There is a place called hutton le hole where we always go, its a bit off the beaten track but it has a stream that runs through the village where you can have a great picnic and the kids can safely play in the stream.
I would say the boredom would set in at flamingo land after about 3 days, althoug there is also a swimming pool there which is good, itsd got a few slides in and a wave pool i think.
Flamingo land would be good for all your brood, it suits all age ranges,
you must go and watch the seal show its really good.
If i am able to get up there I will show you where hutton le hole is would make a good place for a meetup , there is another mnetter going up there at the end of august too what dates are you going??