first of all, what year of ib are you in? lets assume that it is your first year; then don't worry, you have plenty of time to write that ee.
i am in my second year and i spent last summer and first semester of my first ib year searching for a topic and found a nice good one. i changed my topic for 5 or 6 times, so do not worry. i have been writing my ee for 5 months. as i am starting my 2nd year in a month, i am planning to finish writing my ee.
if you are starting your 2nd year, i should better help you on your subject rather than giving you some advice. if i were you, i would choose a narrower subj than vedic maths. i mean it is well studied and there are lots of websites or books about it; so choose a small portion of it and work on it or change your subj to something else. you can study differential equations or eceonomical mathematics.
the comparison b/w square roots in vedic maths. and the normal long division and estimation looks good but make sure you are creative about your work and not just copy-pasting what you find in websites or whatsoever. its unfortunate that i do not know much about vedic maths, just some general facts.