What to do for my parents 25th anniversary of marriage?  

I took my parents to a very nice restaurant. I arranged for music to be played when they cut the cake. I presented my mom with a food processor and my dad, his favorite music album. You can arrange a surprise party with all your family members. Or you can simply give them a gift-travel-voucher of their favorite destination.

I think you should make them like a scrapbook of all their memories while married and relationship from before. I think it would be romantic and they would really enjoy sitting down and taking a trip down memory lane. Also you can make them a nice romantic dinner with some candle light and then leave really fast before they get freaky lol.

On my parents 25th anniversary, my brother and I asked an artist to paint their photo together when they are still young. We also held a small party by inviting our close relatives and Me and my brother gave a touching speech by expressing our thanks to them for all the things they did to us, and how much their relationship has become a role model for our relationship to our partner as well.