Hi u4gotboutdray01,
From what you describe, you assume that you need a reasonably-strong GMAT Score before you ask anyone to write you a Letter of Recommendation. That shouldn't be a factor in who you ask for an LOR - but if someone's LOR is contingent on your GMAT Score, then that's an LOR that you probably do NOT want. For a Letter of Rec to be meaningful, it has to be 'genuine' and full of praise; if it feels 'vague' (for example, if it's from someone who simply does not know you very well), then it will likely be ineffective (as far as convincing an Admissions Committee of how amazing you are).
If you do not think that you will have any issue scheduling a 2nd attempt (if needed), then your original assumption has no bearing on that choice. IF you would only feel comfortable asking for an LOR after you earn a great GMAT Score, then you won't ask until you have that Score - meaning that the 'lead time' for asking for the Letter is irrelevant (re: your GMAT Score would have to come first before you even asked). Based on what you have planned, there's no reason to schedule a 2nd attempt now (it would essentially be an expense that you might be able to avoid).
GMAT assassins aren't born, they're made,
Rich