For sure do both if you can! I think you would learn more at the GPs surgery than the care home, at the latter you could end up just talking to patients and making tea. I get what you mean though that it would be a bit intimidating
just talking to a GP, I got to shadow a junior doc or in a hospital for a day and I just felt so out of place when they were discussing treatment with patients etc. I got to do that shadowing because I did a student volunteering programme at my local hospital, to find it I literally just googled 'Lister hospital (my nearest hospital' volunteering' and it took me to the NHS websit. The student programme last for 15 weeks but there was one girl on a gap year who did it for 6 months. We were given the option to either shadow a consultant for a day or get the email of a junior doctor, I chose the latter and she was really lovely, asked me straight away when I wanted to come in! Although the normal volunteering wasn't as interesting, that was just talking to patients and making cups of tea. Its definitely worth doing the less interesting stuff as it can lead to cool things, like when I shadowed the junior doctor I got to see some surgery (gall bladder removal)! So either do both or go to as hospital as it can be a nice balance between the two in terms of boring vs interesting stuff!