Ok, it can be tricky with more dc with SN than carers.
Take paperwork - for legoland, a dx letter is ok, or any document which states the nature of the disability. You can both get in as carers, no problem. I take my 3 (all ASD) either me + DH, or with an additional carer too, and we all get in as free carers.
The exit pass scheme is trickier. A couple of years back, it was changed and now it is for those 'who do not understand the concept of queuing'. Wheelchair/physical disability won't count, necessarily. Essentially, it is meaning ASD/sensory issues.
The exit pass is for the disabled guest plus up to 3 others. If you get more than one pass issued, they will take pains to ensure you inly have the right amount covered - ie we often get issued with passes for 2+3. They won't issue a pass for 5, officially, although we have had one more than once.
Then it gets tricky as each guest needing an exit pass must be accompanied on rides by a carer/adult. Fine, except most rides at legoland need the dc to be 130cm or over to ride unaccompanied. So eg, we had issues getting on a ride all together as dd1 (tall enough, but severe ASD) needs to be accompanied, ds is only 3 so needs to be accompanied, but dd2 (who had other exit pass) doesn't need to be accompanied (has Aspergers and is sensible) but Must be accompanied on rides if using an exit pass (which we have to as they wont issue an exit pass which covers the whole family!) = logistical nightmare and the reason we often take an extra carer.
Rides at legoland are another issue. Lots are 2 seater (3 at a pinch, if dc are small enough) and the height limit to ride unaccompanied is bizarrely high given the slow-ish nature of the rides (130cm). Given the combination of not enough adults to go 1:1 with each child, and the exit pass not covering all of us meaning we had to use dd2's exit pass (meaning she had to be accompanied on rides even when she was tall enough) -it was quite stressful getting around legoland over the last few years!
It is good, though, just wanted to warn you it could take some planning!