http://www.padawansguide.com/index.shtml
http://jedi-academy.com/costume_tips.html
are a couple of very detailed websites on making various SW costumes. I followed a lot of the advise there, making necessary changes for kid sized, and not worrying about every little detail like seams. Too complicated for me. Like I said, I'm a total beginner with sewing. I found my Obi-Wan fabric at
Walmart. $2.99 a yard. This year I couldn't find it. My son has requested Anakin. So I found Homespun at Joann. More expensive, but had a coupon for 50% off. For Obi-Wan he's wearing his school uniform khaki pants. For Luke ROTJ, he's wearing girls stretch legging from Walmart, just a size bigger so they are not tight and I had to add a draw string so they didn't fall down. Luke's costume is 2 pieces, pants and a jacket with a double breasted type flap. I just used 2 old black turtlenecks and cut a "flap" from one of them, sewed it to a similar cut piece of an old white undershirt and then sewed that to the first turtleneck. Cut down the neck to make it more collar type and Wahlaaa...... The prequel Jedi have 2 tunics and long tabbards over the shoulders front and back. Luke wears more of a vest with short tabbards attatched front only. I happened to have this old ugly long 80's grey sweater type vest and I just tore it appart and used it. You could make it from almost any standard vest pattern and then add the tabbards from the shoulder seams. They are just basic rectangles. The cloak is a biblical costume pattern. For a prequel Jedi, follow the pattern for the robe, but not the hood. It's too small for a jedi. Something adult sized is perfectly oversized for a kid. I found a simple lined hood pattern online.
Shop thrift stores for old belts. Just cut them down to kid sized. My dad does leather work and I just gave him the tutorial for Obi-Wan. Actually when he went to Tandy Leather to purchase the stuff they were very familiar with making SW belts and told him exactly what he would need. Luke's belt is just a 1 1/2 wide black leather belt with a military buckle. I just weathered it up a bit to look old.
The x-wing costume is just a basic cotton orange NASA costume from Target. I followed most of the advise here
http://echobaserebels.com/reference/xwingcostume/ I scored the chest box on ebay for 99 cents. People thought it was a "broken" Darth Vader chest box...because it didn't talk. LOL It's actually an old lazer tag game piece and works perfectly. I added the hoses.
Here are a couple more shots of my mini-Jango.
Or maybe you don't want to show him for fear he'll want one.

I started that costume about mid-June and was putting the last coat of paint on the jet pack the week before Halloween. I started with a Rubies helmet and totally tore it down, replaced the face mask, sanded, painted, sanded some more, painted some more, lined it...then put it all back together. That alone took me about a month. The armor is hand cut, shaped, sanded and painted then velcro'd and/or straps (for the leg pieces that wouldn't hold right with just velcro). Belts and holsters made from rope dyed, leather cut and dyed and some vinyl for the pouches. I did cheat a little on some things like the knees. He couldn't walk well in the handmade knee armor so I switched to knee pads painted silver. The gauntlets are an old Boba Fett toy set painted silver. The jumpsuit is modified from a NASA costume because I was running short on time to finnish one sewn from a pattern. He was 6 at the time and LOVED this costume. It still fits him since he's so skinny at 8.
I am also doing an Indy this year! Not nearly as much fun in the work...but so much easier. I only have to modify the shirt a bit and find and/or make a suitable bag. The rest is pretty much done. No pictures taken yet though. Then I get to start on my Anakin. Have the pattern already, just have to get the time to start on it.
Let me know if I can be any further help.
regards