You may want to check your configuration of the product.  In the product configuration page, there is an entry,

'Selections(orderable quantities) of order quantity drop down list on product lists and product detail site. If this field is not empty the quantity box in module CAT_Cart will be disabled for this item. (press ENTER/CR to separate, leave blank for all quantities, 1 for hide the quantity box and the ddl, 0 for hide the quantity box, the ddl and the [Add to cart] button. Works with Normal and Subscription items.)'

As you see, if you enter a '1' in this box, your quantity box and the ddl will be hidden.  A ''0' hides the quantity box, the ddl and the add to cart.

Not sure if this works for donations. It says only normal and subscription, but it's worth a try. If it doesn't, you can go into the skin and hide the controls by adding

style="display:none" to the table row(s).  Or set the control to 'visible="false"