Is your Airport Express the first or 2nd generation version? The first gen units were not as stable as the 2nd gen units. I currently have 2 Airport Express units (2nd gen) in separate systems and I have no issues with my iPhone or iPad so I suspect there is a problem with your Airport Express or with your network. My iPhone is the latest SE and my wife's is an XR. They both work fine with our Airport Express units.
Your least expensive solution is to purchase a 2nd gen Airport Express which goes for between $30 to $50 on eBay.
I don't think a Bluetooth unit will give you as good a quality as WiFi.
By the way, I auditioned a Bluesound Node2 and found that the Airport Express with any of my external DACs sounded better than the Node2 with its internal DAC. Using my external DACs with the Node2, I could not tell any difference. So the DAC is more important for the best sound quality.
Your least expensive solution is to purchase a 2nd gen Airport Express which goes for between $30 to $50 on eBay.
I don't think a Bluetooth unit will give you as good a quality as WiFi.
By the way, I auditioned a Bluesound Node2 and found that the Airport Express with any of my external DACs sounded better than the Node2 with its internal DAC. Using my external DACs with the Node2, I could not tell any difference. So the DAC is more important for the best sound quality.