Please would you mind shipping directly to me as I am shipping to you next monday
Is it better to use going to, I don't think so because Iam going to do it for sure and I can't use present because it is something I do very rarely.
I actually only learned what this is called recently. It's not a term that's used often, but it's handy for explaining this bit of English grammar. "I am shipping to you next Monday" is an example of a futurate. That is an expression of something that will happen in the future using the present tense.
It's simply using a present simple or progressive main verb with an extra phrase/clause to indicate when. It looks just like a fully future expression, but that "next Monday" is all it takes to make it semantically future time. The following are all practically equivalent:
I will ship to you next Monday
I will be shipping to you next Monday
I ship to you next Monday
I am shipping to you next Monday
For some verbs, there would be a difference between the simple and the progressive, but in this case there isn't, in any practical sense. It's just another one of those little quirks of English.
I can't use present because it is something I do very rarely
I'm assuming that, by "present", you mean the present tense. If so, this is not a reason to choose a verb tense. The tense of a verb is only about when the action takes place; it doesn't have anything to do with how often the action happens.
If you intend to ship something in the future, "will ship" and "going to ship" are both correct:
I will ship the package to you next Monday.
I am going to ship the package to you next Monday.
("Will ship" is just the future tense of "to ship".)
There are some very subtle differences between "will" and "going to". In general, "will" is more confident than "going to" - so if you want to convey that you are certain about shipping the package, "will" is a bit better. But the difference between "will" and "going to" is very small; in almost all cases, they mean the same thing.