This might sound silly, but a lantern archon, with its aid at will, is a surprisingly effective quasi-healer at low levels like that. The persistent magic circle against evil is a handy buff, too. Persistent tongues makes for a translator, and greater teleport at will makes an excellent messenger, remote shopper (got cash for Raise Dead but no diamonds? no problem!), even a party taxi if you have an extradimensional space to work with and it can carry the opening (portable hole, handy haversack for smaller characters, whatever). Sure it's always lawful good, but at Int 6 it's stupid enough to be easily duped or distracted, so it doesn't get overbearing.
Want it to grow up with the party? Give it some class levels. It's got 1 HD and CL 3rd, a few really nifty tricks but nothing overwhelming, so ad hoc call it LA +2 and go to town. Cloistered cleric is an obvious choice for the increased skill points, knowledge domain, and a spell list well suited to buffing and healing, but also consider bard. Its spell list is also well-suited to buffing and healing, it gets all the knowledge skills as well as the bardic knowledge class feature, and not having much of a body doesn't bother it much depending on how you play it. As many physical attackers as you have in that party already, Inspire Courage should be a welcome boost, and if you opt to go the dragonfire inspiration route, when the archon sings so will the rest of the gang.
A word of warning: continual flame at will is a slow but persistent economy smasher. If you go with the archon, remove this spell-like ability, and maybe replace it with another level 2 or level 3 spell-like (one of the cure or vigor spells for unlimited genuine hp healing could be ideal).