Should I raise rates with agent? How much others getting?

I have been doing a lot of work for an agency in town.  They do events at colleges, malls, country clubs, company picnics, and such.  They set up the bounce houses and hire local face painters, balloon artists, jugglers, magicians, etc. for these events.  They have been paying me $50/hour.  My normal rate is $75-$100/hour.  I recently was at an event with a balloon artist who said she charges them $125/hour.  They only hire her a couple times a year.  She has plenty of work outside of them and has been in business a long time.  I did 28 events for them this year!  So I would hate to lose their business if I raise my rates.  But this balloon artist thinks I am worth more and should be charging more.  I do end up turning down other gigs because I'm working for this agency.  But it's also nice that I don't have to deal with any of the paperwork and the environments are always safe and clean.  I'm also in a situation now where I am separated from my husband and need to increase my income to support myself and my daughter.  I was wondering what other face painters are getting from agencies.  Is $50/hour the normal rate?  Or are people getting paid more? Should I take the risk of raising my rates or not? (You can see samples of my work at www.fancyfaces.biz or https://www.facebook.com/FancyFacesOfRochester/.)