If you use beams you should stack at least 2 of them.
To switch the lights on buy a relay board rated for you AC supply. Wire it so that it is activated when one of the beams is triggered. The relay board must have a timer function. I can't post links but search Home Automation web site.
Hi
I live and operate my business in Cape Town South Africa.
Great forum, have found so much usfull information already. Pitty I can't get access to the business section.