Find out the package and benefits before making a decision. Don't forget if you have your baby there, unless he negotiates with his company, it won't be covered by medical insurance, which could wipe out any saving.
If you have your baby in the UK, will you have somewhere to go, and manage with a 4 yr old out of school alone? Will your dh get the time off work? And then you would wait in the UK for baby passport, just in time to fly back for summer, from April its too hot to play outside. Most expats I know, if the dw is not working, leave end June after school finishes and return end August. You should budget somewhere to go every year, unless you stay and go to softplay ( deserted as people leave ) every single day.
Who will let you live with them in comfort with 2 children for 2 months and not drive you/ them mad? Or will you keep your UK house empty and just for your trips home? How does that impact financials?
It might be worth your dh going out, taking a serviced apartment and you staying til next September in the UK, then move out.
Set up costs are very high. Post his package on expat woman, here, or expat forum ( not so heavily moderated as expat woman) and see what people suggest.
Be careful with loans. Your dh company could loan you the money up front for accommadtion, and take it off his salary every month. For cars, you take a loan. You need a good car each. Make sure if he doesn't make his probation you get your money back on the car. Companies notify banks when last salary payment is made, and accounts are frozen to check all loans are paid. They can put a stop on your dh passport at the airport!