Hi Hayley
I have double checked this and can confirm that you are able to do both excursions. The submarine trip has several times against it and is usually booked for 8, 9 or 10am and lasts around 2 hours, the Cultural Centre trip is from 1:30pm-10pm. According to my colleague it is considered a full day because of the duration of the trip - however, she will update this to avoid any confusion in the future (so thank you for bringing this to our attention)
On to the second part of your post there are 36 people booked on this holiday and there are 4 places left so what I say may change....
As you are in your late-twenties, I can confirm that you are the youngest on the trip - the rest of the group is from early forties to mid-seventies. There are 10 men booked and the rest women.
You're not the first to start getting nervous and you certainly won't be the last. I am aware that at least one of your fellow travellers has used the community (I recognised a name of the passenger list) so I'm sure if you post in the "say hello to other travellers" section, you may be able to get in touch with each other - this may help ease some of those nerves.
Have a wonderful holiday
Kindest regards,
Julia