I see several options:

1. change your code to achieve lower delays on the other functions
2. use interrupts at a set frequency to trigger the sending (and maybe the automatic transmission trigger pins, see MCP2515 datasheet, depending on pin use & schematic of your specific shield)
3. use a basic scheduler/rtos

It is hard to tell what is going on witht the rest of your code/if it is a good idea to try to achieve faster functions. I am not 100% sure the CAN-lib would will work well in the context of an interrupt.

I see several options:

1. Change your code to achieve lower delays on the other functions
2. Use interrupts at a set frequency to trigger the sending (and maybe the automatic transmission trigger pins, see MCP2515 datasheet, depending on pin use & schematic of your specific shield)
3. Use a basic scheduler/rtos

It is hard to tell what is going on without the rest of your code, if it is a good idea to try to achieve faster functions.

I am not 100% sure the CAN-lib would will work well in the context of an interrupt.