Gail,
Many forms of Vitamin C can cause "D", in the store where I work we suggest our customers use ascorbic acid "to bowel tolerance only", but a mineral ascorbate form (like Emergen-C) might work nicely. It mixes in water, provides B vitamins, and you can use as little as you tolerate well. It is also an electrolyte source that will help control "D", I put this in 16 oz. water bottles, and use no more than 1 packet a day.
I had so few GI symptom's , my Crohn's was diagnosed after I used sorbital daily for about a month and could not stop the explosive "D" that resulted. It is known to cause "D" and dehydration by food scientist and dietitians, and is (IMHO) a IBD sufferers nightmare. I still cannot use sorbitol, or any sugar alcohol, without bad "D".
I hope you are having a mini flare, as often happened to me following sinus infections, or from the Vit C, and you are well for your trip. Please be well and have a great time with your family.