What is you DS into?
Magic kingdom - very classic Disney films - quite a few non rollercoaster rides (which our 2 year old could go on)
Fab firework show
Animal kingdom - personally not my favourite and only do if we have the time. But with the new pandora area it's quite popular. Has animal exhibits and a safari, few gentle and gel rollercoaster type rides.
Epcot - is a good park to wonder round - some rides very dated but lots of opportunities to meet characters as not so many rides to take up your time. Again another fab firework show- but the current show finishes it run after the summer of 2019.
Hollywood studios- is what it says on tin - movie based fun! Has been a bit of a poor cousin recently with lots of ride closures but set to be very popular from early 2019 when Star Wars opens! Along side the new toy story land which opened this summer. Another great theatre style firework show.
Universal studios - I didn't visit this year so it's a been a while, but from what I hear it's mainly aimed at the teen market, with more thrill type rollercoaster rides.
You the also have the water parks and sea world but given your lack of time I would discount those altogether.
I'm a purest and magic kingdom is what it's all about for me! Seeing the castle, Main Street! You just cannot beat the first glimpse of the castle!!
But it really depends if your DS is into any thing specific? X