My daughter has been on both Humira and Remicade. Remicade has the advantage of being dosed based on weight, which is VERY helpful for a growing child. You also have the advantage of being able to change the dose and frequency. You can only really change the frequency for Humira, from every two weeks to every week.
I know the allergic reactions for Remicade sound scary but not everyone has them and your child will be closely monitored by nurses. Both my daughters have been on Remicade multiple times, which most people say you can’t do (i.e. stop it and restart it). They both have moderate to severe inflammatory arthritis and ran out of treatment options, so had to re-try drugs. My younger daughter has IBD too. They actually didn’t mind infusions when they were younger - it was an excuse to miss school and watch TV, read, nap or catch up on homework! If you go to a pediatric hospital, the nurses are wonderful with kids and most kids like the fact that blood work can be done right there and so it’s only one poke every 4-8 weeks, depending on what your kiddo needs.
My daughters actually preferred Humira though because it was a 10 second injection every other week or weekly and then they were done. They both did their own injections, starting at 13 and 15. Their doctor encouraged that to give them a sense of control and they both were scared in the beginning, but ultimately preferred it.
I do want to add that biologics are very safe drugs and in the 14-15 years my daughters have been on them, they have had no major problems. In fact, my younger one’s IBD improved immensely on Remicade in just 8 months and because we treated it aggressively, it has not been a major problem. The only side effects my daughters have had is being tired the day after Remicade infusions. They had no side effects with Humira.
I also wanted to add that my daughter has had iron infusions several times, though her hemoglobin has never been that low. We were told typically if it’s under 8, they do a blood transfusion instead of just an iron infusion. But anyway, iron infusions helped her immensely when her iron was very low before she was diagnosed with IBD and she felt SO much better very quickly. Hopefully it will be the same for your son.