You need to look at it from a few angles. What are the pros and cons of you going or not within the company. Will it strengthen your position for future roles or limit you if you don't take it. What are your company's views on work life balance? Can you consider taking the role but working it flexibly in line with the new laws that have come in. Maybe doing longer hours for three days per week and and lessening the rest so that you can either spend more time with the kids or fly home more regularly.
I've flown with my ds and had no issues other than a couple of days upon return when he has to get over the jet lag. I'm sure your kids could manage it too if you wanted to take turns with your dh in who does the flying.
Ask yourself and then more importantly ask your dh what he would do in this situation. Don't prejudge. I do it all the time with my dh and boy do I get in trouble for it. He needs to be completely honest about his feelings in the whole situation and you need to make a decision as a family.
Ask the kids what they would want. They may be young but at the same time will have an opinion. I'm assuming you have a nanny who you would be taking with you. 7 mths for the kids would be extremely disruptive without some continuity in their lives. Remember they are resilient though.
All in all my thoughts were that you need to look much longer term as to the benefits this will bring. Obviously consider the long term benefits for you career wise but take a longer look at the benefits it will bring to your family and this may help you decide.
Will taking your kids to another culture broaden them and benefit them? Will they have more opportunities in another country (even if it is for a short time). Consider things like does this mean they will spend more time outdoors at the beach and if so is this a lifestyle you want for them.
Is it worthwhile you going away with your dh for the weekend to talk this through with no distractions. For me that never works and we have better conversations at home in bed in the evening than away but maybe you need this.
Maintaining a relationship is extremely hard at times and requires as much work as your career and raising a child. Remember you are currently managing three very stressful careers those being job, family, relationship. Sometimes things have to give and where ever that is there must be understanding from the other side.
I doubt I've helped at all but being opinionated wanted to share my view.
One last thing, having worked with expats remember that assignments can be extended. Be very sure about the decision you are making and that it is based on the actual time line the company have given you as opposed to one they think you want to hear. Is it a specific project that must end within 7 months or if you work well is there the opportunity for you to stay on out there in another capacity. If so would your dh give up his career. There is nothing to say he can't take a career break and be your stay at home nanny. Wonderful for him and the kids.
In this current economic climate Company's are very interested in any ideas staff have on how to reduce costs within the business. If your husband has a valued job within his company he should be able to take time out or offer alternatives to the company which will see them reducing their cost but not losing him completely. Are there no roles he could telecommute on within his own company thus meaning you are all in the US?