Hi Maureen!
When I lived in Orlando I was childless. My husband and I would walk through the parks and roll our eyes at the crying babies, the pouting toddlers and the tired parents. We always said, "If they get in for free THERE IS A REASON." Well, when I became a parent, I quickly ate those words! (Just like every other thing I thought pre-parenthood!)
I don't think there is an ideal age for Disney. I've been with a 7month old, a 10 month old, a 2.5 year old and a 3 year old (not at the same time, of course!) And each time has been completely magical. I'm pretty sure they don't remember it all (or any of it!) but I remember! And I have lovely memories of every trip with them.
As far as if your 2.5 year old will enjoy it? YES! It will be a different trip than if you and your husband went alone, of course. You'll have to stop for naps. You won't do as many thrill rides. You might not stay out until 10 every night. But the lights? the colors? the giggles? the memories? So much more worth it than a full itinerary!
My very favorite resource to recommend is the
Magical Beginnings Map. You can download and print it at home. It's a map just for little guys. It highlights all the kid friendly attractions in the parks. It will give you a good feel of what your 2.5 year old will enjoy. And what I like to do is find picture or videos of the attractions online to get my daughter excited (and head off any fears) about what she is going to see and experience.
If you have any other specific questions, please ask again!