If your DS doesn't want to go and you can't change the holiday plans, then you may need to cancel (is your DS certain he doesn't want to go?). Even if that happens, though, you've still been really brave in trying to book a foreign holiday for the first time. Plus, now you've hopefully learned some things about doing it that you can use next time to make it more successful.
The "you have 30 minutes to confirm" stuff is just intended to make people panic and book things impulsively. You end up getting better value by taking your time and looking at your options thoroughly, because that way you get a holiday you actually want in a place that's suitable for you. Use a reputable firm and always check the cancellation policy before booking.
Finding out about countries before booking is important. It helps you decide if you actually want to go there, and helps you feel more confident there (for example, by knowing what social norms are expected where, what languages are widely spoken and how to say simple phrases). Some people choose not to travel to certain countries because of human rights issues there or politics.
Travel insurance is a must-have. Not just the basic, tick-box one, but proper comprehensive travel insurance that covers your health conditions and your children's conditions. You have to disclose absolutely everything, too. Some people choose to risk going without it, and are risking health bills of tens of thousands of pounds or even having treatments delayed due to lack of funds - it's not worth it, especially with children.
If you're going to be navigating airports for the first time while responsible for children, it can be useful to contact the airport in advance and ask for assistance. Many airports use lanyard schemes, can provide extra support, and can even organise advance visits so you know what will happen, where and when.
I'm sure you'll have had a lot more useful advice, too. Even seemingly minor things like taking the correct plug adaptors and having photocopies of important documents can be really helpful. These are often things people have learned from experience (I made the plug adaptor mistake myself, actually, the first time I travelled by myself) and you can learn from other people's mistakes to avoid making them yourself.