as long as you have done a school visit its cool..its doesnt matter if u did it after submitting .. since ur visit gets recorded... the ad-com knows u conducted a school visit...
as for campus interviews, I would recommend either of the 2. Now UCLA being a west coast school, it is possible that an alum may not be located in Philly....
I would vote for an alum interview for 2 reasons.
1. cost - makes no sense to come to LA for campus interview.. it would have made sense if u had not made any campus visits, but since u did that already, the additional visit is not going to add to ur profile
2. new interview strategy.. this is the first time ucla is doing the interview after applications.. since the process is completely new, there is no idea of how the interviews would be like if done by ad-com or current students in the campus... so as a precaution it would make more sense doing it with an alum...
my 2 cents.. i am sure kryzak and red can throw in some valuable comments