The kids pools are great.
There are a few playgrounds dotted about the parc that toddler should enjoy.
There is a beach at the lake so bring a bucket and spade to make sand castles.
She can use a toddler trolley in the Parc Market when you do any shopping and be a "big help to daddy"...
Find the wildlife centre and do the walk, talk to the rangers, there's usually some paw prints to do rubbings of and other colouring sheets.
Bring some chalk for the blackboard in the house - to draw, play X/O's, leave notes for each other
Sit in the bbq area of your cabin really quietly and watch the birds and wildlife around the place.
Bring a board game to play and a few favourite toys. I think they have dvd players as well (but it's been a couple of years since our last visit so confirm that from another source) - but could be good if there's a favourite disc to watch at home.
There are some activities suitable for younger DCs which are paid - kids club type things.
Dd loved it when younger and was never bored, we went a number of times. It's only now she's a late teen that it's "lame".