when I tried something like that long back what I did was 1st arrange the diwali light in the background in desired style..put the lens in manual focus and move back at least 10 meters. now move the focus ring and select the desired type of bokeh in the BG...you will notice that the bokeh will become smaller and sharper then will become bigger and dull ...soo select as per ur need
Now place the subject so that its in proper focus ...move it forward back manually
now u will have focus on subject as well as desired bokeh
*farm8.staticflickr.com/7052/6896141689_be91329317.jpg
Valentine teddy by sujoyp, on Flickr
ooh btw if u want to get this heart shape bokeh ...cut a heart out of a small cardboard square piece...and put the heart shape exactly in center of lens ...now all bokeh will be in heart shape ...try new shapes.
*lh5.googleusercontent.com/-cFt1cn-uW1E/TzTuKc81CbI/AAAAAAAAHF0/EPWMBHUkWO4/w767-h685-no/DSC_2772.JPG