This is a great presentation that talks about the risks and the benefits of various IBD meds. The risk of Lymphoma is very small - 2 out of 10,000 in the general population and 4 out of 10,000 on a biologic.
For my daughters, biologics have been miracles. They both have a form of inflammatory arthritis, and the younger one also has IBD. They became close to normal teens once we put them on biologics. My older daughter went from being in a wheelchair to being a normal college student who plays soccer. The younger one is still a work in progress in terms of her arthritis, but within 8 months of Remicade, her colonoscopy showed a "beautiful" colon. Her TI still had a bit of mild inflammation, but there was quite a difference. Her Calprotectin is 26 now!
I agonized and agonized about putting my daughters on biologics but in the end, the risks of the disease were much scarier than the risks of treatment. With IBD you risk strictures, fistulas, abscesses, growth failure etc. and around 75% of patients with Crohn's have surgery within 5 years of diagnosis. Biologics reduce that risk.
Wanted to add that both my daughters say they can't imagine life without biologics. They've had NO real side effects from Remicade/Humira, besides some fatigue after Remicade infusions, which only lasted for a day.
Good luck!