I want to address up front that our family is a-ok with the whirlwind style trip and we prefer it. I build in down time but multiple stops over 2 weeks is good for us.
Next June
The 2 must have spots are London and Paris- these are not negotiable (seeing a performance in Paris and London is just a requirement). Beyond that, I am trying to decide between:
-exploring Ireland (very vague, I know- lots of research to do!)
or
-head to Brussels and Amsterdam
Lots of world to explore and too many good choices.