Kingmaker Group?

So our GM wants to run a 3 man party through Kingmaker, Why? Real life stole a couple members of our group, so now we have 4 players. . .

We are debating pitching the idea of:

1 Half Elf Wildcaller Synthesist Summoner.

1 Half Elf Summoner.

1 Half Elf Master Summoner.

Concept: We are all siblings out on our first grand adventure. All grew up together, went to the same schools, learned the same skills (Class), just all came out a little different.

Rely on Restore Eidolon Lesser for heals until 750 communal gold, the wand of CLW.

Thoughts?

oh, and I am wondering... Can an Eidolon who took the 2 point evolution Ability Increase: Charisma (Now has 13 Cha) and Skill Focus: Knowledge (Nature), take Eldritch Heritage Feat at level 3? I am debating playing the Summoner, and the idea of me and my Eidolon both having familiars (Later Improved Familiars) makes me giggle a little bit every time I think of it...

Bring alchemist's fire. Swarms can be a bit of a bother as a summoner, when your only way to hurt them is summoning air elementals and ordering them into vortex form. (Which requires speaking Auran, as well.)

iirc, wild-caller cant be a synthesist since they both edit the same skill, though servant of the blood god--or whatever it's called--is fine though.

being 50% more summoner than every other summoner and getting to disregard your physical stats completely would be a tad excessive.

oh, and I am wondering... Can an Eidolon who took the 2 point evolution Ability Increase: Charisma (Now has 13 Cha) and Skill Focus: Knowledge (Nature), take Eldritch Heritage Feat at level 3?

The Eidolon doesn't meet the requirement of a certain character level.

It might be allowed, when it has a similar HD, but it need GM approval.