My son is the only one with a costume so far. He's Captain America. That was easy and pretty reasonably priced. I don't have any ideas for my little girl or my husband and I. I hate to spend money on a costume we're wearing for one party.
My kids are all grown and we don't dress up for Halloween anymore but I do have a sugesstion for you. With the one son being Captain America, perhaps the other Avenger characters would be good costumes for the rest of the family to dress up as. You might be able to get "the look" for less money at thrift stores. Instead of masks, face paint would also save you some money as well.
I'm too old to be dressing up for Halloween, but I may dress up for fun. I do have a tip for buying costumes though. See if your local costume shop has any major sales the day after Halloween, aka November 1st. I know that the Spirit Halloween stores sell all their remaining stock for 50% off after Halloween.
Resale stores usually have costumes for sale at a very reasonable price this time of year. I was just at a resale store today in Appleton, WI with my daughter and granddaughter and I was amazed how many Halloween costumes they have for sale. You may want to check out resale stores to see if you can find some at a good price.
We're not dressing up for Halloween this year. We're just having a quiet Halloween at home watching scary movies and attacking a mixing bowl full of candy. I probably will hit the 50% off after Halloween sales to get stuff for next Halloween.
I just recently watched all of the Star Wars movies (the original trilogy, then the newer episodes) and I love it! I can't believe it took me so long to sit down and watch them. I think it would be tons of fun to be R2D2, but it's nearly impossible to find a cool costume for an adult. I think I will probably make one (or attempt to!), but I'm leaning heavily towards a Star Wars character. I'll definitely go out in DC on Halloween night (or at least the weekend before), so dressing up for the holiday is a must for me.