I am not sure such an old iPad will sync to any of the more current versions of iTunes.
Also, that 8 year old iPad may not have a current enough Bluetooth spec to work with newer Bluetooth speaker system.
There is chance iTunes 12.6.5 might work, but it is still a risk.
Why buy an such an old iPad or even a large iPad just to play music?
I do think you would be wasting what little money this iPad would cost and your time if this iPad does not connect with newer software/iTunes.
You are might be better off looking for an older 5th gen iPod Touch that runs a much newer iOS (iOS 9.3.5 ) or bite the bullet and purchase a new iPod Touch 6th gen that runs the latest iOS.
OR,
If you insist on using an iPad, why not get an iPad you can actually use, as well as play music.
There is the new 2018, 6th gen 9.7 inch iPad with Apple Pencil support.
A 32 GBs storage WiFi ONLY model costs $329 U.S.D.. A 128 GBs, WiFi ONLY model is $429 U.S.D..
If you can find older iPads that are NOT Activation Locked to purchase, any older iPad that can either run iOS 9.3.5 or 10.3.3 or even the newest iOS 12 maybe somewhat cheaper than a new iPad.
With older iPad models, stay away from 16 GBs storage models.
Only look at 32 GBs , 64 GBs or 128 GBs storage models in older iPad models.
Good Luck to You!