Please help with this career decision!!?

I honestly wouldn't say that you are screwing over anyone. You have to do what's best for you and if it means taking a better job offer than let the company A know that's why. They might see you as so valuable that they'll do a little bargaining (more money, better hours etc). However, I understand completely your situation. I honestly would go for the job with more money and flexibilty. It's so hard to find a job that has both those aspects so take advantage. If Company A can't cater to your needs, then do what's best for you! Good luck!