I think the most low key bowel cleanse would be drinking psyllium husk in juice 4 or 5 times a day for a couple of weeks. I did that for 3 weeks (it's a long story) and got a real good bowel cleanse, with no bad side effects to me or my breast fed son.
I've also done Dr Schulze's intestinal cleanse lightly when ds was 3 months old (only did the cleanse, and ignored his diet ideas) and ds never showed signs of problems.