It was wrong for your husband to have made the decision to go without discussing it with you first so YANBU to be annoyed about that.
However if the package is good enough it may be a perfect opportunity for your family. Your husband will be earning a fair amount so you can afford to have decent holidays (and being in the Middle East its much easier to travel further East/South), accomodation will be bigger than most people in the UK have and its likely utilities will be included. Depending on the company his hours may be better than he has now, government organisations in the region often work 7.30-2.30 and there are more holidays to look forward to.
Moving into the unknown is always scary but you can adapt. Your husband will get a school allowance to enable you child to go to a decent school, under your husbands sponsorship you maybe able to find work otherwise there will be chances to volunteer etc.
Being in Saudi it will be more restrictive though things are getting better. Wearing more conservative clothing, even an abaya (long black cloak thing) and scarf isnt that bad though you wont have to wear it everywhere anyway. You do NOT have to go out with a chaperone as some have suggested.
I have lived everywhere else in the Middle East except Saudi and as a woman definitely felt much safer than I do in the UK and certainly didn't feel like a 2nd class citizen and had the same sort of lifestyle as I would anywhere.... if not better due to having more disposable income. I could meet up with friends (male and female) for coffee, dinner and where allowed, a few drinks. Gyms were often totally single sex so no grunting, sweaty smelly men getting in the way lol, beauty salons are as cheap or as expensive as you want so manicures etc every week is doable if that's your thing.
I have had female friends and colleagues who have happily worked in Saudi and yes there are issues at times... paperwork being the most frustrating, or adapting to things being closed at prayer time but they've generally enjoyed their 2+ years and come back with a fair amount of savings.
I do think you need to give it a try at least for a year or 2 and then if it doesn't work out , you'll have some savings and as a family can decide on the next step.