I had the same questions, and found this thread on search.
I'm leaning toward using the Barbara's coupon or
Amazon since it will be just me and DD (now 10 y.o., and I am so glad
Legoland considers her still a "kid.")
My follow up questions:
(1) I never heard of Barbara's before this. I don't see anything that says I can't just buy the tickets on the site and take them to the park as normal tickets without needing a box of the cereal. Is this right?
(2) Oh, I guess I should confirm (being paranoid and all that, since we are leaving the day after tomorrow), that these are just tickets you print at home?
(3) DD will want to do the water park.
Does anyone know for sure that I can pay $15 at the park pp to add the waterpark while we are there? (Even if I go with these discounted tickets.)
Barbara's fine print reads " Offer cannot be applied to pre-purchased, other online ticket sales or combined with any other discounts or offers. No photocopies or facsimiles will be accepted. Additional restrictions may apply."
The Amazon Local fine print says "Cannot be exchanged for any other type of ticket or combined with any other offers or discounts."
I just don't want to end up with Legoland only tickets that I can't upgrade at the park to include the waterpark or I'll be in super hot water. I already forgot we had an early release day at school this week,

so I had better not screw up again!
If there's a chance I won't be able to buy the waterpark tix there, I'll need to get the
AAA tickets instead, but they are more expensive and I have to go on the cheap.
TIA