The Monster Cross looks really fun! 50 miles sounds intimidating but I know I could handle the 21 miler. Our wedding anniversary is that Saturday but maybe we could turn it into a weekend getaway and do something fun Saturday night. I'm going to bring it up to hubby tonight. I'll also check out the other links you posted.
I have never done the Wild Goose Chase before but have been planning on it for this year. However, I just found out that the St Michael's Running Festival is also that weekend, so I might run in that on Saturday instead and just do the fun ride on Sunday.
2007 Trek 7.2 FX
2015 Felt F85X with Specialized Oura seat, Specialized Road Pro II handlebars, and Look Quartz pedals