Excellent start.
A game I'm on called idle champions has the following weekend event that they announce on Thursdays.
Special login random chest
Special bonuses for specific classes. More damage or coins or experience
Special chests that appear just for the weekend
In this game items and equipment loads in the chests.
The good thing about it is I spend 1 min to just nab the weekend chest, but ultimately stay for 1hr to collect those weekend special. If I miss that weekend, it's ok. At least I keep an eye out every thurstay on my email for special events.
I do recommend a full list of specials if this is going to bend a recurring theme. That way, people can prepare around these weekends without the need to point fingers.
Some specials I can think of
1. Double or triple coins drop
2. Double book loads and spell learn
3. Double rank Xp
4. Double triple Xp gain
5. Double eq load rate
6. Double spell circles
7. Double melee damage
8. Double spell damage
9. No bash day
10. Improved invis day.
11. Triple health day.
12. Haste day.
13. Diablo event day. Heal potion and word of recall potion sold in store