After some consideration, I thinking that after spending the night in Fussen, we will just tour the grounds of Neuschwanstein instead of embarking on the craziness of a tour with our 2yo. The reviews of the tour aren't great and with the stairs and trying to contain a toddler, it doesn't seem worth it.
However, I am curious whether a tour of Hohenschwangau might be better? 30m is a great length for us and it sounds like there are just the two floors with more inside to see (being that it was actually lived in). Would anyone have suggestions or recommendations on touring just Hohenschwangau and walking over to Neuschwanstein for the photo ops and to see it close up? How long does it actually take to walk between the two (assuming we avoid the bus or carriage)? We will have a stroller for the longer walking for my son.
We plan to do the castles in the morning and leave for Salzburg early afternoon. That means I'm hoping to dedicate just 2-3hrs to the castles (long enough for my toddler). Does this sound reasonable?