Pasadena - large group
I've held several large parties at Saladang Song. You may want to pre-arrange a prix-fixe menu with 3 or 4 items to be served family-style. That way, you can come in close to your budget and still offer a variety of dishes. But if I recall correctly, they do offer lunch specials that are reasonably-priced.
Also, Radhika's (next door to Green Street) offers a lunch buffet for around $10. It's a great site for kids, bc of the nearby shopping arcade and fun British telephone booths.
Daisy Mint probably can't hold a group of 30 anyway...
I second Saladang Song.
Also consider driving a little bit to Arcadia area and go to one of the Asian/Chinese places there. Lunch is super cheap ;) Of course, the ambiance will not be nearly as nice as Saladang Song and such ... but consider Newport Seafood, Phoenix, etc.