We didn't take our great niece to WDW for Gay Days this past year, but we have taken her to MK and EP several times now. The first time, she was 13 and a half months old and we are planning to take her back on Sunday and she will be 18 months old then. We really enjoy our trips with her because it's so much fun seeing the parks through her little eyes. She loves Princess Tiana. Each meeting with her has been so magical. The first meeting with Mickey Mouse was awesome too. She was in awe. She constantly hunts hidden Mickey's in books and around our house. She's a Mickey nut already, which is totally fine at our house.

MeMe is what she calls Mickey and MeHe is what she calls Minnie.
The thing to remember about taking a baby at that age is that the visit isn't about the rides, but rather about spending time as a family and enjoying the experience with your little one. This will not be a vacation, because you will still be Mama. You will still be changing diapers and all of that stuff, but honestly, I think it's so worth it. Plan on bringing extra changes of clothes, some favorite snacks, sippy cups with extra fluids, a stroller, a special huggable stroller buddy, some small toys/books, a wet baby washcloth in a ziploc bag (trust me, it can be a lifesaver), and your sense of humor. Be prepared to let your little one walk up to the characters, because we have found that if we hold the baby, she tenses up around the characters, but if we just let her walk up there, she's fine. So far, no rides that are "safe" for her age and height have been problematic. She loves to fall asleep in the Haunted Mansion, so obviously she's not disturbed by it. lol Try to keep the baby on her schedule as much as you can, but realize that nap times usually do get off schedule even with the best of plans. Just take those nap times as a chance to enjoy each other, ride a thrill ride, or maybe even snooze a little too.
Be prepared to have magic happen when you least expect it. The last time we took her to the MK, I was waiting for my partner to come back to me in Fantasyland because she was taking the stroller to the drop off point with the baby who had decided that she wanted to walk for a while, while I finished shopping. The baby loves music and she stopped suddenly in the middle of Fantasyland and wanted to dance. Gabby joined right in with her. She said that she didn't even realize that music was playing, but she enjoyed her dance with the baby with the busy crowds rushing by. It was just one of those moments that you can't plan, but it's magical and priceless. Also, the baby loves to wave and blow kisses. It was so much fun watching her blow kisses and create smiles on faces of other guests all through the park as she did so.
I do agree that if you want to make sure that you have a sit down meal, please do be prepared to make your reservations as soon as your booking window opens. The Plaza Restaurant at the MK is a favorite of ours. The place is small and feels more intimate. We all love the food there too. Other MK favorites include Cosmic Rays, Casey's Corner, and Pecos Bills. Over at EP, we haven't tried any table service with her yet. We will one day, I am sure, but for now, we really enjoy Sunshine Seasons.
If there is any thought in your mind that you might want to get that PhotoPass cd, just go ahead and purchase it a week or so in advance and save the roughly $50. Even as locals, we are finding that it's hard to go and not want to by a PhotoPass cd. There is just too much magic that they capture so perfectly to not buy the cd.
If you and your partner want to go to Gay Days for more than the gatherings at the WDW parks, then leave the little one with family or friends and go do Gay Days in style. You will enjoy it more and there will be no worries about exposing the little one to potentially inappropriate stuff.