Should I wait or pitch?

I made 5 gallons of an irish red ale about 36 hours ago and it still has no signs of fermentation, but I also have a 1 gallon batch made from left over wort that I pitched harvested yeast in and it started fermenting very quickly. I know I should wait 72 hours, but I am leaving for a week in a couple hours. My question is should I wait until I get back to do something, or pitch as much of my already fermenting 1 gallon batch into it.

Also would it be safe to mix in the 1 gallon batch because it has a different strain of yeast?

Also is it safe to wait a week before I take any action?

What yeast strain and what is the ferm temp? Starter or no starter? How old was the yeast you pitched?

It was the irish red ale from wyeast, with no starter and about 6 weeks old. Not sure about the ferm temp, but it is at 65 degrees right now which I thought to be pretty standard.

You should be fine, I think your are a little under pitched. If you are leaving for a week I would use a blow off tube set in a sanitizer solution so if it takes off big while your gone you won't come home to a beer mess. With a blow off tube in place the beer will be fine for the week you are gone, the 65 degrees is about perfect.

Thanks, If i come back after a week tho and it still did not ferment, could I add more yeast or is it pretty much ruined?