Hi Ruth!
I have a VERY active 1.5 year old, too! I know the terror that can ensue when he isn't happy! So, YES I think a 1.5 year old will LOVE the Playhouse Disney show. It is interactive, the kids sit on the floor, they can jump up and dance and sing. All their favorite TV characters will be there (but not as scary as the costume characters because they are puppets and much smaller!) singing their favorite songs. Honestly, I love it as much as the kids!
The Little Mermaid is a little different because it has lots of blacklight effects and lazers. Not to mention Ursula who can be quiet scary. So, it depends if your 1.5 year old is frightened easily. You do sit in chairs in rows so, if you need to get out quickly, you'd want to sit on the end!
Besides these shows (and the others) there is Honey I Shrunk the Kids Movie Set which is just a big fun playground, Muppet Vision 3*D and the Pixar Block Party! Not to mention, just running around the Studios is fun and exciting to me!
Don't forget to check out the
Magical Beginnings map designed just for the younger set--including your 1.5 year old!