Hey!
Congratulations on the multiple VS offers!
This is definitely a tricky situation, and I had a similar issue last year where I was invited to a final TC interview post-VS but it clashed with a second summer VS that I was completing (+ the first firm had no flexibility with interview dates). Fortunately, the firm I was completing the second scheme with let me have the morning off the scheme to go attend the interview, so I would double-check with the firm to see if that is a possibility (as some firms have policies for this!). However, if not, I don't think there is anything stopping you from attending the VS for the experience