Oh boys, very brave idea.
I understand your effort and costs for running NDR events, but I think that if something is OPTIONAL it`s doomed. On the other hand, many of LFS racers are unemployed/students and it was hard for them to pay for S1/S2. Do you really think they would "donate" to participate?
I think it would be better if you try some kind of sponsorship first, and if that fails, you can ask for donation. I`m sure that there is someone that could help you host the servers, vent....
Another solution is cutting the costs, maybe organize less leagues.
One more thing, offer some kind of partnership to ones interested in organizing LFS events, share costs, have less work,....
Your events are very well organized, I enjoy participating (when my connection works
), so if "donating" means NDR survival, you shouldn`t wory about money, it will come.