I totally agree with Lil; don't worry too much about making choices now that will see you through the rest of your working life. It is perfectly possible nowadays to make a dramatic career change after several years (I am currently doing just that!) so don't worry about it!
Unfortunately in the current economic climate there's no such thing as being 'ensured a good job', so my advice would be to take options that interest you and that you'll be enthusiastic enough about to get good grades in. Once you've got through your schooling, you'll have plenty of time to worry about your career choices! Good luck