you can definitely mix real and fake plants, but you should be very selective what real plants you choose, as some need more light, CO2, and/or nutrients than you may be providing.
Are the bulbs from Wal-Mart? They commonly sell bulbs for tiger lotus and apogneton. They are pretty dense (both the bulbs and the Wal-Mart employes), so the guppies nibbling at them shouldn't have an effect unless they are nibbling at the new growth