Hi lazynewt from Scotland
You haven't told us where you are based, as this makes a big difference to any rural business you can hope to succeed. For instance, intensive veg relies on good soil, good climate and a nearby large market, which can be restaurants, box scheme etc. I must admit that I started off with that intention, but we didn't have TAS back then, so no-one to warn me! In fact ill health decided for me that working myself to an exhausted wreck for tiny returns just wasn't for me.
Our own children were fledging when we came here, but for you, you are doing this for your family. An exhausted, bad tempered Dad the children hardly ever see, isn't going to make them enjoy their lives.
Is there anything in IT you can do from home? That way you have a steady income of whatever size you need, you can choose to do the computer stuff when it's pouring outside, and organise your life around the important work on the holding, leaving time for the family. It's important not to take on everything yourself, but to take that little bit of extra time to let everyone else muck in.
From the cash flow angle, whatever you decide, there's going to be a fairly long time between you arriving at your smallholding and actually being able to market anything you produce, so keeping one foot in IT seems an excellent insurance, which can be scaled down as your smallholding income increases. Think of this as being for your family too - something you just have to do in order to keep the new life afloat.
There is a huge amount of knowledge and experience here on TAS, so you've come to the right place. Do take time to read all the other threads on this topic, as it saves people the time needed to repeat themselves.
Whatever you decide, keep us in the loop. New smallholders have so much excitement and enthusiasm that it's great to read about it - cheers me up anyway