it is very difficult because although it is partly an emotional decision, it also has to be a practical one. I don't know which country this is. I do know that things are very difficult still in Poland and I would worry about moving there for that reason. You do want to know that your future and the future of your dc is relatively secure. It would be hard to give that up to go somewhere knowing that you could end up in quite a bit of financial difficulty. The Polish people I know sadly cannot realistically return home, although they own property in Poland, they cannot earn enough to live there.
Hungary I would consider if dh has a job that is in demand and would provide enough income to support everyone and put some savings aside for the dc's job training/higher education. In Budapest you could earn, if you work a great deal and mostly privately, a reasonable supplemtary family income with teaching English. If dh were to leave or die early, you could be in serious trouble unless you have an emergency fund to get you back to the UK and a good chance to find work in the UK after your time away. Things can go wrong anywhere of course but Eastern Europe doesn't provide much of a safety net.
Moldova is desperately poor, I don't think even with a strong altruistic bent, I would risk it with the dc to worry about. So many dc are left there behind while the parents have to work abroad. Romania I don't know about. Ukraine would be difficult. Would be a hard life unless dh is likely to be earning a very high local wage. People still have to hold down two jobs to make it sometimes.
Croatia might work, due to all the tourism. You might find more of an option there.
Depends what dh does, what he can earn and how you think you could cope if left there on your own with the dc (if things did go really badly pear-shaped). You know that in case of divorce, you might not be able to leave with the dc, depending on whether this country is signed up to the Hague Convention. If dh were to refuse to allow it, you would be abducting the dc if you upped and left.
What do you do? Is it transferable once you have the language skills to work there?