Regarding the value of a tax deduction:
$800 of donations would save you between zero and $200, depending on your income, and whether or not you have enough other itemized deductions (like state and local taxes and mortgage interest) so that you are already taking the itemized deduction on your tax return. If you are not already using itemized deductions, then $800 of donations is likely to be of no actual tax benefit to you.
Regarding receipt requirements:
If you donate items with a fair market value over $500 but less than $5000, you need a form 8283, but you do not need signatures from the charity or an appraiser. The documentation requirements are on page 20-21 here,
https://www.irs.gov/pub/irs-pdf/p526.pdf
What the IRS says, is that for donations less than $250, you need your own list of items, in sufficient detail that someone could determine their fair market value, and a receipt from the charity. A drop-off receipt is acceptable as long as your own list has sufficient detail.
The the IRS says that for a "deduction" of between $250 and $500, you need a written acknowledgment from the charity, but they also say that you must have separate acknowledgements for each donation over $250. This creates some confusion as to whether, if you made two donations of $200 each, do you need to follow the rules for donations under $250 or the rules for donations between $250 and $500. I will say that I personally have never gone so far as to ask the charity for a specific acknowledgment, but I have not been audited. I have seen comments on this board from people who were audited where a drop-off receipt was not enough. What the IRS really is concerned about, is can you prove that you actually donated the items on your list. I donate to Goodwill and they give a blank receipt that has all the details required except a signature from the charity. I think that would suffice for the IRS if I could get someone from the charity to sign either the receipt (that I can staple to my inventory list) or sign my inventory list.
For donations over $500 but less than $5000 you need the same information, except that your inventory list should also have the approximate date you acquired the item and the approximate price you paid. You can make your best guess--the point is to show that you paid more originally than the value you are claiming for used items, and unless you are donating collectibles that you claim have increased in value, I don't think anyone is going to have a problem with you claiming a reasonable value for a used frying pan as less than the cost new.
So what you really need, is a detailed list of items, and a signature from the charity that you really donated the items on that list. I would call ahead, and try and talk to a manager about how they handle this type of situation. If they insist that they don't provide signatures but "it's ok", then it's up to you whether to make the donation or find a different charity. Certainly lots of people donate with simple receipts and never get audited, and I do that myself. But the IRS written rule is that you should have something from the charity acknowledging that you really did donate the items on your list. (The charity will not provide a specific value, so don't ask. You will determine that later. You want them to acknowledge receipt of your specific items.)
