What specifically is the Shaymin event? You must give me details when offering so I know what is being offered, otherwise I cannot accept an offer, sorry. I have some Shaymin events already, so it may depend. Unfortunately, I'm not too interested in average Shinies unless they are also competitively viable.
Okay, so I can trade them for 4 events, possibly these if you're okay with that.
Kotone Yasue's Shiny Tyranitar (2015)
Pokemon Scrap Venusaur (2016)
Pokemon Scrap Charizard (2016)
Pokemon Scrap Blastoise (2016)
It's okay, no worries. Just offer me the same number of legitimate events and it'll be fine. I'll consider doubles of certain events, too, if they have competitively-viable natures. (: Mistakes happen. I'd definitely be careful as to where you're obtaining and trading your events. A FB group is likely not as trustworthy as /r/pokemontrades, for example.