Do you know if the Dev's have tried approaching the big Bitcoin businesses and asking them for their solution? Because this is the biggest threat to their business and as far as I know they make a lot more money than the mining pools so they should have the upper hand.
Donating coins to p2pool is certainly possible and there is a donation address for it, but it shouldn't really be necessary because p2pool already does better than centralized pools by reducing orphans, paying out transaction fees to miners, allowing merged mining and not charging any fees. So hashers who adopt it and become full miners should already increase their earnings.
The bigger issues are: 1) awareness, 2) easy of setup/management, 3) compatibility with some mining setups (some specific ASICs don't work well and very small miners won't get consistent earnings). If you want to help with decentralization, contribute to working on one of these three items. Anyone who is interested, even without any programming or scripting ability, can help with 1).