Entertaining a 9 year old girl. HELP!!?

For the next 3 weeks my boyfriend and I will have both of our daughters with us (we're both divorced and have one girl each from our previous marriages) and they will both be with my during the day while my boyfriend works and then i will work nights. The problem? His 9 year old wants to do NOTHING but play video games, PC games, and watch TV all day. My daughter is the complete opposite....wants to run, be outside, blow bubbles, swim, go to the park, read books, etc. Granted my daughter is 6 years old and there's three years between the two of them. How can I spark the 9 year olds interest to try anything? She doesn't want to read, bake, play board games, play cards, or do anything that requires physical movement. I'm concerned about her lack of inactivity, but her Dad tells me to leave her........she's happy. Really?? How can a 100 pound 9 year old be happy? I do not want drama and defiant activity during the time I have both girls due to their lack of differences in interest. HELP!