To answer your questions:

1) yes, mix it, should be fine.

2) yes, as long as someone keeps them watered as necessary.

They probably won't even be up that much in 10 days. Should work just fine.

No, don't mix it. Instead you should layer it. Fill the container with potting mix, then a dusting of the seed starting mix, next sprinkle on your seeds, then top off with the seed starting mix to bury the seeds to the right depth. That way you use the seed starting mix for what its designed and the roots will grow just fine into the potting soil.

You'll get MUCH better results if you heat the soil to about 75-85 degrees. Mine germinate from a depth of about 1/4" in 3 days. I use half a strand of Christmas lights (about 20 watts) in a box, insulated with a blanket. A baking rack sitting on soup cans holds the containers above the lights.

I always pre-moisten the soil and usually don't have to water for at least 7-10 days after planting. I've killed more seeds with too much water than not enough, it should just be damp. I keep it covered loosely with plastic for the first day or two but that's kind of risky with fungus and all and I plan on experimenting without that in the future. I also microwave the soil to 190F in the planting container.

I think you'll be fine without watering for 10 days if you're using seed starting mix. Maybe plant half your seeds now and half when you get back just to be safe?