D750 - Shooting 150+ event

Hi everyone,

i will be shooting a event with over 150 folks mostly family and friends. I am also hosting this event with lot of help from immediate family. My main gear is nikon d750 and tamron 24-70 f2.8. the venue is indoors with lot of natural light, huge windows and lot of lights inside also. The ceiling is about 30 feet tall. I did a test run today and bouncing flash off the ceiling is not an option.

I am sure many or at least some of you have shot events that you hosted where one has to multitask socializing and taking photos so here are my questions

1) Ill have my tamron 24-70 mounted on d750 primarily. Should i use the flash or just let the d750 do its magic? (great shadow recovery and high ISO performance) I also have a 17-35 wide angle lens. its a family event

2) i am pretty much by myself with taking photos with may be one more person familiar with photography. how do i balance things out with taking photos and socializing

3) any particular settings you suggest for indoor with lot of light from windows? (white balance, metering and fstop)

Thanks a lot in advance!