Hi,
Monday shouldn't be too busy at the busy, providing it's not in/near school holidays (however this is Legoland).
In terms of rides, get Boating School done first as it's a night,are to queue for and has reached 30 minutes+ in the first hour.
Also get Laser Raiders, Atlantis, Digger, Dino Dafari and Squid Surfer done at the start of the day also.
Do Vikings and Pirate Falls midday and leave Dragon til the end of the day.
In terms of food, I'd suggest City Walk (pizza & pasta) otherwise Knights Table is a good alternative (I haven't done burger kitchens yet).
Ascot may be on so be prepared for long waits whilst exiting the park which are often a problem at Legoland anyway.