Vicky - I completely understand where you are coming from with this one.
I work full time and have for a number of years - DH used to work part time so he was the "main" stay-at-home parent. After our youngest went to school he went full time so I really know where you are coming from on the childcare thing.
I often work very long days and luckily travel less now but used to be away frequently. That was hard. The practicalities can be a challenge LOL. However, I knew this to be the case when I accepted the job so I hardly feel I can complain! I think you are taking a really sensible approach and weighing up all the pros and cons
Basically it is as others have said - it's about chosing what is right for you and your family. Is the sacrifice worth the extra money, is the question I guess.
If it feels right to you, then go for it! You can always change your mind if it doesn't work out for you -
nobody would think any the less of you.
Good luck to you. I wish you well!