They don't always load the reservations for the dessert parties at 180 days like all of the other restaurants, so often you have to keep checking, but I've never had an issue booking once they do open. The plaza garden Viewing has become a little more popular than the Terrace version because of the better view from the garden. You watch the show from your dessert party table at the Terrace party. We did the Terrace party the first time I saw Happily Ever After and I was so disappointed that I couldn't see hardly any of the projections.
It's not that crowded. The tables are a little close in the upper portion of the Terrace (where you eat the desserts), but the Garden didn't feel crowded at all. It's nothing compared to being apart of the sardines on Main Street. I think it's a really fun, casual way to end the night without having to fight the Main Street crowds.