Asking senior scientists for a subreview
You can always ask and they can say "no". It's surely not rude and weird; people are asked to review stuff all the time. The probability is not too low that one or more of them will say "no", but you may be lucky. 

In my experience, more senior people are more likely to say "no", but of course if they say "yes" they will be the more competent reviewers. And some say "yes". 

Don't be worried about asking somebody something that they don't want to do. If you ask and they say "no", it won't reflect in any way negatively on you.