Hi! I'm looking to build a broodmaster that has all of his eidolons take teamwork feats. He may/may not dip into a standard summoner to get a huge "siege engine" eidolon if that's possible, and will probably dip into bard to get a couple songs to boost my eidolon party. My idea is that he'll be great for solo adventures, considering he brings his party with him. What do you guys think? Is this viable?
I don't believe you can take the same class twice. So if you take broodmaster you cannot "dip into a standard summoner".
Hm. If I can't, would this still be a valid build though?
Teamwork feats with your eidolons would work, except for the annoying problem that your entire brood shares a single pool of feats, which is small enough that you wouldn't want to reduce it further by dipping into other classes such as bard.
You are probably better off taking the standard summoner class and forming a tag team with a single eidolon. That single eidolon would have almost enough feats to keep up with the summoner for teamwork feats, or more than enough if the summoner takes Extra Evolution at every opportunity.
If you want to dip into bard, you may want to take a look at the Lyrical Summoner prestige class in d20pfsrd's "Into the Breach: Summoners". That prestige class is designed for a bard/summoner multiclass.