I would go on Friday if I were you. (or - go twice

we went on Friday and then again on Sunday last year and will do the same in about a month)
The rest of the park is very quiet (from my experience) but round the corner leading over to Star Tours and you will be blown away at all the fans and characters roaming around. (nothing like hearing "make way for the Emperor" and seeing him walking through the crowd with his Royal guard with him). We didnt stand in line for many autographs of pictures but while the boys napped in the stroller, I parked us right outside of T.Traders and just watched the characters walking by. The "less known" characters simply walk around (including storm troopers, clone troopers, some bounty hunters, the Cantina band plays on the corner by Star Tours, etc) and they will stop for pictures and autographs if you ask. The "bigger" stars are set up with lines just like Mickey and crew are in the other areas of the park. (I saw Boba Fett, Chewy, Kit Fisto and Mace, Queen Amidala, etc) Every weekend there are one or two actors there signing autographs and they give out a limited number of fast passes to get those actual autographs (these guys were set up over near the Backlot Tour area) so if you want those autographs, get there quickly to get a fast pass or to get in line. There is a great Star Wars only parade (I want to say it was at 11 in the morning) which my boys loved!!! Also, don't miss Jedi Mickey - he is in the place where Mickey usually is stationed down beyond WWTBAM and that was a GREAT photo Op. WWTBAM is Star Wars themed for the weekend, but I haven't gone in there. There is Jedi Training next to Star Tours that is fantastic for younger children (maybe up to 10 or so) and when they are dont training, last year both Darth Maul and Darth Vadar came out and they got to do their moves again them, one on one until all the padiwan had a turn.

(I know - I am such a geek)
For the person asking about Fantasmic, it will be busy that night, but you can certainly get in without a ressie. We went over about 7:30 for the 9 show and got great seats on Friday night.
I agree with NotUrsala, the wait for Star Tours seemed very short every time we saw the sign. I would consider it walk on (15 minute waits).