Probably too late now, but I would have insisted on first a complete rebalance of the tires and then 6 new or different tires as a test long before I started spending money on other replacement parts.
If as you say your shake started as soon as the new tires went on then then it stands to reason that the tires are the cause. Hopefully you and the shop have some kind of good working relationship. Ask them to hold on to a set of appropriately sized tires removed from another coach and give you a call. Take the coach down and swap tires and go for a drive.
Or have them replace one tire and swap it to all different tire positions on the coach with a test drive between swaps. This test isn't as accurate since you could have more than one tire problem, but it is a start.