If you aren't ready to buy a machine right now you could try using your free motion foot along with your largests needle and heavy thread...just be sure to use heavy cut away stablizer.

I have an embroidery machine and I enjoy using it a ton. However for your project no way! It would be too expensive, the learning curve too steep and the frustration level off the charts. To use one of these machine takes lots of practice, many trial and errors and lots of expense. For a project this size I'd do hand embroidery and/or writing with fabric pens or paints. Ask friends with embroidery machines to see if they would like to take on the challenge in trade or for payment.

If you get an embroidery machine be sure to get it at a place that gives you free classes to teach you how to use the machine.
I have a Bernina that has the embroidery module, but I've never used it! Embroidery by hand is really easy. Honestly. You can do titles in the stem stitch easily.

I didn't think I would ever want an embroidery machine, but the Disney Princess designs were tempting me for quilt for GD. I bought the Brother PE500 for $250 and am having a ball. I have to admit to eyeing the bigger ones with larger formats, but am sticking with Brother due to the Disney stuff.

Didn't need to take any classes, it was pretty much plug & play.

My mother used to save her dryer sheets to use as stabilizer.

You could enlist the help of a friend or as my daughter did, teach yourself to embroider. And there is always a good excuse to buy a new sewing machine so do whatever makes you happy. I hope you share this with us as you work on it or after it is finished. I have a little Harry Potter fabric and am planning a quilt, but not the project of doom. It sounds great. Good luck.