They might start off by requiring guests wear masks, but I am willing to wager that they will have to relax that and make it optional within a week. There will simply be no way to enforce it widely.
I've also noticed a phenomenon in our city where, once the city council decided to REQUIRE employees and patrons of essential businesses to wear masks, the physical distancing COMPLETELY disappeared. People think the masks make them invincible and so it's now impossible to go into Costco or a supermarket and stay 6 feet away from everyone.
I worry about such ignorant behavior. The fact that that kind of carelessness is obviously common here in the US is what makes me worry that openings (both of the parks AND other venues) will either not happen any time soon or will be followed by a new surge of infections. Opening right now (before there is a vaccine) relies on widespread acceptance of both masks AND distancing. Anything else is not backed by evidence, I believe, but an expression of wishful thinking, and is unfortunately likely to result in more deaths.
Maintaining mask and distancing compliance is probably easier in Shanghai and other Asian countries, where people seem better informed about the public health effects of not wearing masks and not distancing. Apparently there is far greater public consensus about judging somebody’s not wearing a mask (or getting too close to people, either with or without mask) as careless, rude, and selfish.
Here in the US, on the other hand, there are people who are turning mask wearing (or lack thereof) from a public health issue into a political statement, and that attitude and the behaviors it comes with worry me. I hope that the people who feel so strongly about masks being part of some conspiracy and seeing being ordered to wear them as an attack on their Constitutionally guaranteed liberties will decide to boycott the parks, if Disney remains strict about this. Problem solved...
I remember similar problems happening every once in a while in the past with the occasional pro-gun fanatic being outraged about their “2nd amendment rights being violated,” when told at security that they couldn’t bring a gun in.
As to people having delusions of invulnerability and getting (accidentally or deliberately) sloppy with distancing when wearing masks... one would hope that people will, over time, learn to change and be more mindful of which of their behaviors are risky and will then be motivated to do better. It would be very arrogant not to. This will probably take time, though.
Regardless of how mindful people are about distancing and how good they are about wearing masks, there will be a remainder of risk, especially in a theme park with lots of different people who traveled there from lots of different places and a disease that presents asymptomatically but still contagious in a relatively large number of people. It appears that aerosols are only one means of contagion. Surface transmission is a big problem, too, and there are limits as to how thoroughly cast members can wipe and disinfect any surface that is being touched by more than one person.
As to smaller kids... as far as I understand, most municipalities’ mask requirements are only for kids of age four years and older and for adults, and since kids can still transmit the virus, I would definitely avoid the parks and other places with large gatherings of people, if I were medically fragile or otherwise vulnerable to dangerous complications of the disease, until there is a widely available, safe, and effective vaccine.