If you are going to traverse Yak in May I hope you have a high tolerance for soaking wet, partially snow covered granite slabs. You could probably have more fun climbing at Squamish in the rain
I would suggest some lines like maybe the Joffre Couloir on Joffre, North Ridge on Baker, N face on Shuksan, NW face on Matier, north arete on Cayley, etc. can be fun May type climbs. In late May steep south facing rock like the south face of Viennese can also be snow free and mostly dry.
Eaton Peak can also be good while there is still snow over the bush. But did someone say - Mountaineers?