If you are within the 30 days of purchase you should be able to return with no issue. This is why the Meraki motto "Try before you buy" is a great idea to run everything in production as you would so you know all your needs will be met.
I am not a fan of the built in wireless in the MX devices as it is limited.
If you have no other options you could try an MR20($300) attached to the MX to get the Splash Page options you need.