It sounds like you’ve got a great variety of experiences already! I think students often over estimate what’s meant by “hands-on”; all medical schools mean by that is for the experience to be something you’ve got yourself involved in in some way rather than just being an observer as it often is with shadowing. You might have simply been chatting to the patients or brought them their meals (as I did when I volunteered at a hospice). I think instead of focussing too much on the hands-on aspect it’s more important you try and secure some form of long-term experience. You mentioned the primary school that you’ve spent time in, even that would be enough if you’ve done it for an extended period of time as I imagine you would have spent your time interacting with the children hilt you were there.
Remember your experiences don’t have to be solely in a medical setting and for most students they aren’t – you can easily demonstrate the same skills required of a doctor (teamwork, communication etc.) from other settings. Your volunteering experience can come from any field and the primary aim of it is to show commitment.