Not to want to rain on things...but I'm not super keen on the whole pledging concept in general.
Maybe it's just me, but my pointed little head views it as an added layer of complexity coming between the individual and (hopefully) their making a donation. And the pledging process tends to come across as being just a little full of itself after a while. Almost like when people try to pep up an otherwise dull meeting by introducing some "team building" activities into the mix.
I don't mind being asked to make a donation to something I admire or believe in. Just let me write them my check or give them my card number and all's well AFAIC. But when they start with games, and pledges, and fund matching 'challenges', and tiered membership premiums, and...well
...all the usual crap PBS layers on top during their bi-monthly fundraisers, I start getting annoyed. And tend not to contribute as a result.
But again, maybe that's just me.
Whatever gets decided, please do your best to keep it as simple as possible?
If there are too many pledge options for a contributor to look at, you run the risk of "candystore lockup." That's when the number of choices overwhelms the customer - who often leaves without buying anything.
Top restaurants know that. Which is why some of the finest and most successful have what to some would seem like an extremely small menu (2 specials + 3 entrees max). Contrast that with the average multi-page jumbo-sized diner menu - and the number of people who end up just ordering a snack or coffee because the menu was too much to think about.