So sorry to hear your news, what a beautiful boy.

Can I suggest maybe calling the vet and asking them for advice? They would be very experienced in this area I would imagine and might help you second guessing your decision if you aren't sure. Another option is to bury the ashes, or keep the ashes in a special box/urn if you want him close by. The vet clinic could help organise this too.

We lost our baby fur boy at aged six to cancer, it's such an awful thing to go through. Thinking of you