many cutters can use different brand blades- each different size is a different cutter- you can not use a 60mm blade in a 45 mm cutter- or other way around---or an 18 in a 45 ect...each blade needs to go in the cutter (handle) it fits.
as for your quilts-if you want to make other's besides baby quilts anything up to about 63"x80" which would fit a twin bed- will work- you can make them 45"x54" or ... what ever they are all appreciated.
as for your tax question----if you want to use your donations for a tax deduction you HAVE TO KEEP ALL OF YOUR RECIEPTS! you are only allowed to claim what you actually put into the quilt- you need reciepts to back up your claim. you also need a tax receipt from the organization with the (claimed) amount on it. you can claim your batting, ect- but you can not claim a 'market value' for the quilts----only what you put into it- it is pretty difficult to claim much when using scraps---and being able to back up your claims- but the batting/backing/thread could still be considered....good records are a must.