the question is ...would she like something like that for her RL engagement ? if yes, then go ahead with your idead, as many people as you will ask they all will have something good or bad or in between to say, this decision can only be taken by you and her nobody else, and you know her enough well to know if she will like something like this or not.

if you have a house you can do it at your own house.....invite your friends to your own house and in the garden make the proposal with all forms and stuff and coordinate with a friend to drop to your /Her RL house the real engagement ring that you of course have bought right ?...

I am not a huge fan of huge stuff I prefer the intimity but if that is something you will love to do..by all means....nothign forbids you to do it !!! we all take chances in life right ?

In the end, this is a UNIQUE moment, something that you have only ONE chance to do and it best be GRAND see what I mean ?

Good luck

Mei