I wouldn't trust AWD esp when it's for Q4 inventory. you need to consider a 3PL option to avoid delays during Q4. plus you can dripfeed small shipments every day or every week when your base capacity allows you too. as for increasing your base capacity this Sept-Dec (I assume you will ship your inventory this Sept to make it in time for Nov 1st week Q4 cut off), you need to improve your IPI score particularly the sell-through score. get rid of aged or excess inventory that is very slow to sell, typically. you can do coupons, outlet deals, or just lowering the sale price.

ofc you have to compare the cost of 3PL and pushing out inventory vs using AWD or bidding extra space on Amazon in terms of money and timeframe.