My DF proposed at Disney in June. The only thing you might need to consider is that they automatically give you buttons at check-in now, so if you have a note on your reservation they will probably hand you the buttons right away which would ruin the surprise.
I had booked everything for our trip, so there were no notes about engagement on anything. We wore our pins everyday and got many congrats. It was so nice, it was like being celebrities. We did get a few special little things. We were staying at the Grand Floridian and they did send us champagne and a card from Mickey one night. We got a few personalized menus, sometimes the tables were decorated, generally a nicer view at dinner. They brought us champagne at Hollywood Brown Derby. At Tutto Italia they sang us a celebration song and brought some extra whipped cream and man that cream was good, not sure if we were supposed to eat it but we did

. I think they would have given us dessert but we were on the DxDP, so dessert was included anyway. At Sci-Fi they gave us souvenir cups with caramel popcorn and a card from the staff. That was really sweet and so unexpected!
So yes, sometimes they do little things to make it more magical, but mostly it's just the extra attention that is fun. We also did the Princess Breakfast at Norway and the princesses all made a big fuss over my ring, so that was really fun. Also be sure to go visit Minnie Mouse. She loves to look at rings since Mickey hasn't gotten her one, it's really a great interaction!
The thing is you can't expect anything, but that just makes what does happen extra fun. The only time I thought we might get something was when DF was cornered in the Emporium in MK by one of the CM's. He made us get the bride/groom hats and took pics of us in them and made us reenact our engagement and then he pretended to marry us. After that he announced us to the whole store, but he got a few things wrong and it was really embarrassing. I thought after all that he might give us the hats...but no.

So if someone corners you in the Emporium, run!
Have an awesome trip!