I want to offer a free event with an optional £5 donation. I can set this up easily with two different fee amounts, but it won't allow me to have the zero amount as the default which I feel is appropriate for an optional donation. I always hate it when a form has an optional donation pre-ticked and it actually discourages me from donating. How can I get round this?
You can do this with Webform CiviCRM module! I whipped up some screenshots for you to show you how. Participant Fee is entirely by Donation in this case. I registered twice: once leaving the Participant Fee at $0 and once deciding to donate $40 (in which case the user gets prompted to enter credit card details; in the $0 of course they don't).
I've now found two ways round this!
First I noticed there is an extra radio button at the top of default column for price options (with no indication of what its for and that allows no option to be default, which is actually better for what I want as it means people have to make a choice to go for the free option so at least consider the extra donation.
Second, I find that I can do exactly what I asked in the question if I use a radio button in a price set.