you do not need a special foot to sew a 1/4" seam, lots of people never break down and buy a 1/4" foot. remove the foot from your machine, put the needle in the down position, measure from the needle 1/4" and make a little mark; run a piece of tape along the mark giving you a 1/4" guide line to follow. (some people use something fairly thick like a piece of moleskin as a guide. i have been using this method for 10 years. i have read so many posts of ... my 1/4" foot is wrong....well, instead of depending on a tool that may or may not be correct making your own guide you know it's right :)
if you choose to use a larger seam allowance you really need to go through your pattern and 'do the math' to adjust every piece. it only takes 4 seams for you to be off a whole inch if you sew 1/2" instead of 1/4" it adds up fast. better to find your 1/4".