Usually people use magnets as temporary signs. It’s a convenient option when you want to remove a sign from time to time. For example, when some company subcontracts a professional (home inspector, roofer, electrician etc), usually they don’t want this professional to advertise his / her business and vehicle signs should be removed.
In your case it looks like you are going use the signs all the time, right? If so, why not to go for a vinyl application? We can print an image on adhesive vinyl and cut out a circle shape. This option is less expensive than a magnet sign. Let’s compare:
2pcs 12″x12″ magnets with full colour print and circle cut are $60.00 and
2pcs 12″x12″ vinyl stickers with circle cut are $30.00 only.