twice. We had our first ever trip to WDW planned and my MIL was operated on, put on life support, and we had to decide what to do. Our entire family wanted us to go as that would have been what she would want us to do. The way it worked out, we left for WDW the day after we buried her. We felt really strange doing it, but it worked out for the best. My DH felt better about the whole thing, and it got my kids minds off of losing their Memere.
Then, 3 years later we had a trip planned to Maryland. My father wasn't really ill, but he was planning to go in for bypass surgery soon. He said to me one day, "if anything should happen, I don't want you guys to miss this trip to Maryland. I know how much you've been looking forward to it." A few days later, he had a massive heart attack and died. It was hard, but we did go, and once again, it was nice to get away.
I really feel our loved ones want us to go on as planned even with they're ill. Ultimately, you have to do what you feel is right in your heart, but I really don't think taking your family on this trip would be wrong. Your kids deserve it as well as you.
Best of everything to you.