xp: turning down a promotion?

prncsstp

Warning - this may be long, so if you make it to the end, and can offer some advice - TIA!

 I work for a microbrewery. The brewery itself is 1 hour and 45 minutes away from my house, but currently, I work from home. My current position is considered "tele-sell manager" and requires overnight travel from time to time. As I am pregnant, I have spent and am spending the last and next month or so travelling more often, so I can see my accounts before I go on maternity leave.

My company has offered me a promotion to "key accounts manager", meaning I would be responsible for all the chain grocery store activity pertaining to our beers for the entire east coast. The job is also home-based, but the travel requirements have been very vague when I asked about them. My boss told me that overnight travel would be minimal, and in most cases, I should be able to fly down and back  from chain locations in one day.

However, I spoke with the current position holder of this job, and he insinuated to me, that at the very least, upfront travel might be heavier, because I ill need to walk through the chains to get a feel for their stores, plus meet with key account managers at our wholesalers, before even setting up appts with the chains themselves. He said to me "if you travel once per week - you will be a rockstar". 

To me, one day of possible overnight travel per week with a newborn is too much.

On top of everything else, this promotion would only come with an increase of $10,000 in pay. And, my boss mentioned that they may want me to keep my current job AND take on the promotion for this $10,000. I told him, that definitely wouldnt be worth it, because I would then be doing two jobs for only a minimal pay increase. So boss-man then tells me that  I would only have to do my current job until they found a replacement (last time I did two jobs for my current pay - it took them 6months to find someone new)

So I think I want to decline this promotion - DH is completely supportive of me. I know that the company will be disappointed, but I know they really value me and my work there, and so im not worried about losing my job or anything..... 

So, how is the best way to go about tactfully declining a promotion? I was thinking of saying something along the lines of:

"Thank you for the offer, I am grateful and flattered that you would consider me for this opportunity, but unfortunately, with the upcoming birth of my first child, I don't think this is the right time for me to venture into a new position"

Thoughts? Advice? Am I hurting myself if I dont take this promotion?