We're going to Disney in a few weeks, and doing all 4 parks (bought a five day pass because it was basically the same price. ) So now we can spend an extra day in magic kingdom if we want. my girls are 6 and 2. The two year old turns 3 in April, so everything she does at the park is free, including her specially prepared gf meals. We went when our oldest was 3.5, and she loved it! We only did 1 park because she was only 3, so she was fine without a stroller for the day. But we're renting a stroller this time because they'll get pretty tired with such a busy week. You can reserve fast pass ahead of time now, so that you won't miss whichever ride or experiences are most important to you. I found it really easy to find fast pass reservations for the times I wanted, I just had to be patient (or obsessive? Maybe that's a better word).
It's totally worth it to us, but it can be expensive. Buy ponchos at a dollar store so you don't waste a bunch of cash at the park if there's any bad weather. We went in January last time, so I have no idea what to expect this time, weather wise.
My girls are really into everything Disney, they must get that from their mom. Lol. So that probably helps in deciding it's worth it. It reallyis very magical. Disney does an excellent job with their parks.