We had a Palo brunch on the Disney Dream & imagine it will be similar: several different sections with fruits, cheeses, pastries...the waiter gives you a "tour" and there is a display of the entrees (specially prepared egg dishes, etc) of which you choose one to order, then you go around and serve yourself the rest. There was a lot of food! I don't specifically remember alcohol but would say it was likely available.
Someone else posted about "will it get me on the ship faster" to try & book....not sure how they work it at the boarding desk, (DH thinks the boarding numbers they give you are random LOL), but after you board, you can go at a specified time to one of the lounges (it should say in the Personal Navigator that you get before boarding) and try to book Palo/Remy dining, if there are any slots left. It is easier to get a dinner reservation than a high tea or brunch one, because there is more availability...tea/brunch only on sea days, and they limit how many people they seat. When we did tea on the Disney Dream, there were only about 10 tables occupied. (it was pretty nice - but still ranked 2nd to Grand Floridian's Garden View Tea!). We also saw someone w/ gluten-free tea menu and that was quite nice as well.
Just checked: 1st Sea Day (day 2 of cruise): brunch & tea sold out, dinner at P or R available; 2nd Sea Day (day 3 of cruise): brunch sold out, tea & both dinners available; 3rd Sea Day (day 6 of cruise): Tea sold out, brunch and both dinners available. I did not look to see if P/R dinners were available on the non-sea days, but imagine that they are. I do not know if they keep back some reservations for those who don't book ahead so worth going to the sign-up when you board to ask...