Yes I concur that it is a one day park. However, you will not necessarily see everything in the day so I would suggest that you research the park a little and have an idea of the things you want to make sure to do and a plan a little bit of a schedule. I find the park to be a little spread out and the layout a little confusing so I think a little research really helps your day go smoothly. Their site also lists all the minimum and maximum heights for rides so it will help to know what everyone can and cannot go on.
The first time we went, I googled
Legoland planning and took some of the advice I found there and found it to be helpful.
Definitely look at the Interactive Park Map found on their website.
My children's favourite area is Fun Town so we always start here. I also think that most people go left or right when entering the park and Fun Town is more into the park so it is less crowded here first thing in the morning.
The Volvo Driving School and Junior Driving School is here and the Skipper School which is my children's favourites. We also love the Police and Fire Academy for family fun! The Sky Cruiser is also here and it was suggested in many reviews that if you want to enjoy this attraction, do it first as this attraction tends to have the longest waits.
My children are older than yours so Duplo Village was not much interest to us but there are some attractions here that your 2 year old can go on.
We always leave Miniland for last as the crowds really don't matter here as it is just looking, except for the Coast Cruise which seems to handle crowds well.
Have fun!