We took our son from the East Coast all the way to
Disneyland at 11 months. It’s really hard for me to imagine bringing a kid under 6 months, ESPECIALLY to Walt Disney World. Disneyland is just so much better set up for children under 5: the hotels are all a short walk, there’s no parking, no buses, no folding strollers, the parks are physically smaller (pushing a stroller is a lot!), the weather is more appropriate to keep a child outside for long periods of time, and the parks are open longer giving you more flexibility in going when it works for your kid. You can also leave more stuff in your hotel because it’s close enough.
Leaving the park for a 90 minute nap at WDW takes about 4 hours including walking to the bus stop, waiting for the bus, taking the bus, walking through a massive hotel property, nap, walking back, waiting for the bus, taking the bus, waiting for security, and on and on. Disneyland a 90 minute nap takes 2 hours and 10 minutes.
Obviously DL is not an option right now; with WDW I’d really suggest under 6 months will be a struggle to have a good time.
They won’t really enjoy it until 15-18 months so before that I’d suggest you try to maximize parent fun while you still can.