I'd take him to the vets. It's an additional cost but then the job is done, he can stay happily with his mum with no worries about what he might get up to!
I had my boys done at the vets last year after it became obvious the Burdizzo hadn't done the job. I was glad I had, they stayed with their mum and sister til they were 8 months old and went to the butcher, so had a really nice life with no stress to me, them or their mum.