Try CAA, Airmiles.
Watch over on the California threads. Often someone will have Legoland kid's free with adult coupons. I also saw something about McDonald's having a $20 coupon.
Often in SoCal fast food places will have coupons. Last year or year before Carl's Jr's had LL coupons and McD's had kid's get in free at SW.
If you have a Costco card you can buy tickets for most attractions at a discount, there's a Costco a couple miles north of DL, another 5 minutes from LL.
I would not try to do LL & SW in the same day. Mainly because they cost approx $70/adult and they're 45 minutes apart. Depending on when you're going, LL closes early (8 maybe?), SW open til 10 or 11PM, until mid Aug then the hours shorten.
Depending on your kids ages, SW starts adult tickets at 10, LL at 12. It was a sad summer when DS14 was 11 and I had to start paying adult prices for him.
SW is our favorite place, we've had silver passes for the past 8 years. We go to SD every summer and spend most of 7 or 8 days there. With the passes it's great to be able to just go for a couple of hours a day and still do other stuff in the area. Love LL too, we haven't been for 2 years but I think it's so beautiful and relaxing.
Have a great trip.