Hi M.,
The Calloway's Fall Festival is this weekend (10/7) and it's at all locations. I'm not sure how 'fun' it will be for a 5 month old...as the activities are geared toward older children...none the less, they have a great area for pictures! The pumpkins there are AWESOME too <and I should know!>. Many different varieties and sooo cute! My next suggestion is the pumpkin patch in Flower Mound. GREAT photo opportunities and the cutest little cauldron that says "My first trip to the Pumpkin Patch" <or something like that> where you could sit him in and take a picture. VERY cute. They also have character cut-outs where you can take pictures. Best of all it's FREE. We do it every year and we always have a blast!