Order Fulfillment Options - dropshipping effectively

[chetnet]

Hi All,

I've researched for my answer(s) til I'm blue in the face yet still haven't found exactly what I'm looking for, so here I am.
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We have created a new yard game, and still need to raise funds, etc, and do plan on using shopify when ready.  We are trying to nail down the fulfillment process.  Our U.S.-based manufacturer will be shipping directly to U.S. customers only, based off of the orders we get in Shopify, so basically dropshipping, right?  However, they are fairly new to this and we don't want to hound them by sending individual customer order emails for fulfillment.  We were hoping we could export orders via .csv, maybe every 100 orders or so (or once per week for example), they label and ship, and send us back similar of what's been fulfilled.  We then update shopify either manually or automatically?  We assume we can still integrate our shipper(s) rates without issue.  We will be talking with them also to see if we can manage it better thru them (where our supplier logs into our UPS business account for example and ships accordingly). 
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What we are trying to find out is what are our top 3 options to do this efficiently and cost effectively?  Note that we can't use Shopify Shipping Network as our box will be 48" long and approximately 35lbs. (Plus we can't ship this product twice)
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If someone can provide us with the solution, which we end up using, I promise I will not forget!
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Thank you very much for reviewing!
Chet