Family Inflatables in Holmes Corporate Center off of 420 is a great option. Peace A Pizza in Springfield (in the shopping center with Outback Steakhouse) has kids parties. Michael's craft stores do parties. I also hear that Putt Putt in Springfield has a reasonably priced package. Last year we did Chuck E Cheese (Springfield) for my son's 4th birthday party and the kids had a blast. I've also been to nice parties at Kehler's gym in Broomall and I know Delco Training Center in Woodlyn also has reasonably priced parties. I do not know if you are a member of the Ridley YMCA or not, but they have various party packages. Finally, for my son's 3rd birthday, we did a party at McDonald's in Havertown on West Chester Pike. (They have an outdoor play area) It was the most reasonable of the parties I've had and the kids had a blast! Cake, invitations, etc are all included! You may also want to check out Bette's Family Fun Center in Aston, Moonbounce Adventures in Boothwyn or Linvilla Orchards...other great party locations!
I see you are a stay at home Mom. Are you involved in any local MOMS Clubs? I am a member of MOMS Club of Prospect Park. There is also a MOMS Club of Springfield. I am not sure where exactly you live, but if you are interested in more info let me know. MOMS Club offers playgroups, MOMS Night out and more!
Happy party planning!!