I mean, has a vet tested both horses to be 100% (not 80%) okay to breed without passing on diseases or conditions that will kill your foal?
Because it's extremely important that you do that before you breed. It's hard to hear when you really want a foal, but in all honesty, breeding is not something where you can cross your fingers and wait and see.
To maximize the possibility of both mare and foal surviving, research before breeding is essential.
For bloodlines, I was wondering if you could tell us names. Some lines, such as Impressive, are infamous for HYPP, as mentioned before. If either horse has such lines, it's important to test for HYPP and be 100% sure (again, not 80%) that they are completely negative.
Speaking of which, are both horses registered?
If you don't even know why you want the foal yourself, maybe you should take the time to think about that before proceeding? If there's not a reason to produce another horse, then you really shouldn't.
I hope, for both your horses and your own sake, you think this through before acting.