There is a workaround to using both the iPad and iPhone for streaming without rebooting and/or repairing aids or devices. I figured it out by reading other posts on this forum and confirmed it with Oticon. I've been using it for several days now and it works consistently. I decide to post it in its own thread so that people do not need to peruse a long thread to find a solution.
1. Make sure hearing aids are individually paired with the iPhone and iPad following Oticon directions and that Bluetooth is turned on by both devices.
2. When you go to use one device for streaming (say the iPad) and the hearing aids connection is being held by another device (say the iPhone) and the device from which you want to stream (say the iPad) cannot take control of them, go to the device that has control (in this case the iPhone) and switch OFF Bluetooth by swiping up on the bottom of your iPhone and selecting the Bluetooth button. This releases the hold on the hearing aids. You can immediately turn Bluetooth back ON on the iPhone so you don't forget.
3. Go to the iPad and start streaming. The sound of the iPad should be in your aids. If you find that it doesn't start streaming to your iPad or the streaming is only in one ear, then turn Bluetooth off and then back on on your iPad. (This also seems to work if you lose streaming later on in one aid but not the other.) If you find that you forgot to do step 2 before trying to stream, you can simply turn Bluetooth OFF (and then ON so you don't forget) on the device that controls the hearing aid. As soon as you turn OFF Bluetooth the connection is released and the streaming to your aids will start on the device you want.
I share this because I was messing with turning my hearing aids on and off, my iphone/ipad on and off, and repairing my aids. None of that is necessary. Although annoying and one should not have to manually turn off and on Bluetooth, it does work and is easier than the routine I was using before.
My routine now is to always turn Bluetooth OFF and ON on my iPad when I'm done with a video streaming session so that the iPhone can readily pick up. I don't do that with my iPhone as I stream more on my iPhone than my iPad and usually have my iPhone with me when streaming on my iPad, but rarely have my iPad with me when I'm using my iPhone. Technically this is not necessary as sometimes the device can take control from the other device, but I find this less frustrating and works with how I stream and use the devices.
I called Oticon on this to ask if they had a plan to fix this control issue. They said that an Apple change is needed in order for the device to release the hearing aid Bluetooth connection, that we wouldn't need an OPN firmware upgrade, and that an Apple release should be all that is necessary.
Hope this helps others.