For my daughter's birthday, one of her friends brought her a goldfish in a little plastic one gallon tank. I wasn't particularly excited about this, and I knew enough to know (but not much more, as you'll see) that these were terrible for the fish, so I went to PetSmart to rectify things. After some discussion with the salesperson, I ended up going home with a new 10 gallon tank, a filter, a heater, some dechlorinating solution, a couple of plants, and four fish--a Betta, and three neon tetras. They seem to be doing ok-- swimming around, eating, and whatnot, for what it's worth--but some really quick research is now telling me this was really a bad idea. So, fully realizing that, but also realizing I can't just get rid of the fish and whole setup now, what should I do? I'm happy to do some reading, but unfortunately, work and other obligations are going to prevent me from doing much over the next few days, so can you give me a few quick things to minimize the damage and suffering of the fish?

Another wrench, but possible benefit, is that I'm headed to the inlaws this weekend. My father in law (who is not at all a reader, wings everything he does, and I'm quite sure follows none of the rules) has a thriving 30ish gallon aquarium that he's maintained for years now. I read that it might help to take some sort of substrate from his tank to speed up cycling? Good idea?

Leaving the fish for two days - is that ok at this stage? Or should I find a vacation feeder?

Water changes - 10% daily? Is tap water ok? Do I need to add the solution any more?

Would more plants help? How long should I wait to add more fish?

Any other emergency measures that will mitigate the impact?

That damn goldfish is still in that damn plastic 1 gallon tank. I really don't know what to do with it. Can it go in the larger tank with the others?

Like I said, I'm happy to do some reading if there are recommendations, but I'm really short on time these next few days, so a few quick tips would be really helpful.