Moonspeaker Stuff:
Level 1- Augment Summoning. This saves you two feats if you start at 9+, or you can forego the typical Augment Summoning routine altogether, and instead just focus on summoning Elementals with Rashemi Elemental Summoning into Moonspeaker. That routine comes online later, anyway.
Level 3- Extended Summoning. The big drawback of summon spells is their very short duration, this handles that.
Level 4- Invisibility on your list, which is awesome for Summoners (you almost never attack directly), and expanded SNA lists.
SNA 3- Triton, which casts SNA 4 as an SLA.
SNA 6- Bralani Eladrin, which isn't that impressive, but it can really take a beating with it's Blur and Mirror Image SLAs.
SNA 7- Nymph, which has 7th-level Druid casting.
SNA 8- Lillend, which has 6th-level Bard casting and music.
Level 6- +2 Wisdom while not shifting, because let's face it: you picked the +2 Wis trait.
...and that's about it, really. Shifter Druids have sub-levels that give up most of the typical Druid boons in order to really focus on summoning and spellcasting, and you really can get some ridiculous summons out there if you play your cards right.
Of course, if you decide to, instead, enter with Spirit Shaman... oh boy...