You are absolutely right when you say we need to take gardening more seriously. We as Adventists have been counseled and counseled as to why we need to know how to properly work the soil and care for the things we grow in it. It is very sad to see not only public institutions but Adventist institutions getting away from the practice of teaching young people the simple techniques of raising crops. For as you said, if there were a time in which we need to know this stuff more then ever, it is now. many will find themselves facing extreme hunger during the little time of trouble. Hunger that could have been avoided it if counsel had been heeded. Sadly I see many yielding to the beast power just because of appetite.
Now back to your post. I do want to say that having your seed trays in direct sunlight may or may not have been the problem. I just want to emphasize that I have seen seeds get cooked in soil before that was located in direct sunlight. But again a few factors can contribute to failure. You have to remember that a dark soil like what a good soil mix should look like will heat up faster due to being dark. And as well a few degrees temperature variation in the environment they are located in can maybe be the tipping factor in the temps getting to high.
It is nice to have a bottom heat source but not a must if a few of the guidelines listed earlier are heeded, but the bottom heat seems to make the germination a little more uniform. I like the idea of the warm water as a heat source and have thought about that, But what I use are heat cables located in a bed of sand. You can do a Google or Ebay search for soil heat cables and see what I am talking about. But for a small home gardener, you could as well use a heat mat that is made for plant trays. You can get a single flat size mat that would let you start a few seeds that need planted early and then work your way down the list of plants that need started. Like I say, it is mainly used just to achieve germination so A small mat for $30 or $40 dollars might be worth it. You think about it, if you plant a standard 10" x 21" flat on a one inch grid, then that means you will have around 200 seeds in one flat. So for most home gardeners this would be the way to go. I use the heat cables under sand so I can germinate 6 or 8 flats at a time, but again this is according to my needs. I never found the electric heaters to be that bad on electricity for you have to remember they are just trying to maintain a bottom heat of around 75deg.
Now for some different varieties. for most home gardeners that want to start there own plants I suggest you find your exact planting zone which can be found on line and as well try to follow the recommended time the seeds need planted before the last average frost date in your area. If you buy packets of seed, they will sometimes tell you that info, or you can do a online search for the info as well. My first seeds to plant are peppers, lettuce, cabbage, celery, pak choi and broccoli. Peppers seem to need a longer period of time to develop into plants ready for transplant, and the cabbage, lettuce, and broccoli grows quickly but can be set out in cooler temperatures. I have had Chinese cabbage with snow on them that went on to develop nice heads so just know the characteristics of what you are growing and if the seed was bred for the application (spring, summer or fall planting). once these are up, I will plant a few tomatoes for some early ones and after these germinate it is about time for the main crop and as well the Oriental eggplant, and any herbs you might want like basil and such (By the way herbs were my specialty in the plant retail business). After these have germinated I will sometimes plant me some hills of early cantaloupe in pots. I use the plastic bag pots made for this type of plants for you do not want to disturb the roots on these plants so you just cut the gallon pot off the soil/root ball after placing it in the hole. I like flowers to but again follow the recommended planting times for you zone.
Now with all those plants for the garden and your spring planting complete that, you would think that should be all seed starting you would need. May I suggest after all your planting is done and the radishes are being picked and maybe the edible pod peas are starting to set on, that you break out the seed trays once more for what you will need for your fall and winter planting. Like fall cabbage, cauliflower, kale, Brussels sprouts and the like. As a matter of fact it got down to 14 deg the night before last, but I still have cabbage, kale, and brussels sprouts out in the garden ready to eat.
As you said Mr. Myers we do need to get serious and I hope those that read this will at least glean some ideas to further there knowledge and understanding of the God given program for a better mind, body, and spirit, gardening. God bless