G.B.
Sometimes getting too much fiber is hard on them too. Our pediatrician has us give the kiddo's Miralax every day for 4 days when they're blocked up. If it's bad they drink it twice per day for 4 days then drink it once per day for up to 10 days.
But they have blockages than can get to the point of possible surgery. I'd ask the doc if Miralax is something they'd be comfortable prescribing.
We mix it in grape Koolaid and the kids drink it right down.