I just love [name_m]Everett[/name_m] with [name_f]Mary[/name_f] & [name_m]Jack[/name_m]. It seems like the most cohesive in terms of style. [name_m]Francis[/name_m] fits well, too.
And for girls, I would vote for [name_f]Alice[/name_f]. [name_f]Clara[/name_f] is another form of your daughter’s middle, and [name_f]Jane[/name_f] is the female form of [name_m]John[/name_m] (Jack).
But since you asked for other suggestions:
[name_f]Addy[/name_f]
[name_f]Cecilia[/name_f]
[name_f]Eleanor[/name_f]
[name_f]Elly[/name_f]
[name_f]Emilia[/name_f]
[name_f]Evelyn[/name_f]
[name_f]Hannah[/name_f]
[name_f]Lindy[/name_f]
[name_f]Lucy[/name_f]
[name_f]Lydia[/name_f]
[name_f]Maddy[/name_f]
[name_f]Madelyn[/name_f]
[name_f]Matilda[/name_f]
Nora/Norah
[name_f]Olivia[/name_f]
[name_f]Sally[/name_f]
[name_f]Vivian[/name_f]
[name_m]Archer[/name_m]
[name_m]Connor[/name_m]
[name_m]Dean[/name_m]
[name_m]Lewis[/name_m]
[name_m]Logan[/name_m]
[name_m]Rhys[/name_m]
[name_m]Theo[/name_m]
[name_m]Will[/name_m]
[name_m]William[/name_m]