Quality vs. Quantity?

Hi there, I put together our first postcard mailer this weekend and was hoping to get some feedback on the most effective way to use this medium Our company rents arcade games to offices for their break rooms and we wanted to microtarget HR directors at tech companies in our area by sending out postcards.

Since we're on a budget and our target is relatively narrow, we spent the time to hand write our pitch on the back of the postcard, to hand address each mailer and personally address the mailer to a carefully cultivated a list of human resource directors, that was cross referenced by the number of employees that they have and the types of industries that would be amendable to offering this type of workplace benefit. (tech, marketing firms, video game publishers, etc)

We started by sending out our first 100 and plan to send 100 per week for 10 weeks and then gauge our response rate. After dropping the first 100 in the mail, we're optimistic about our chances, but I was also a bit discouraged by how long it took us to write and hand address just 100 postcards.

In looking at our approach, I wanted to get some feedback to see if this seems like the best way for us to go about advertising in this way. Would it be better to save the hours of labor by using preprinted labels/pitch that are addressed generically to HR departments on bulk business mailing lists and then send out more of them or should we expect enough of a higher response rate with the handwritten cards/cultivated lead lists, that it will make up for giving up my weekends to take on this project? (I've attached a copy of the front of our postcard if you have any advice for improving future iterations of our mailer) What do you think that average response rate would be for a bulk mailer for our services vs. something that is more personalized, but time intensive? Thanks for the advice.