My mum is self isolating for 14 days before my due date (ELCS) so that she can look after my DD. I can't therefore see an issue with her holding the baby when I get back - she will most likely give us a hand after it's born for a few days too, and will just be going between her house and ours (not going in any supermarkets etc either).
The problem is DH's family. Three of them are living together and they just aren't taking it seriously. They're mostly adhering to guidelines but I wouldn't trust them to self isolate, for example - his dad is in an at risk group for age and health issues and is still going to the shop every day for the paper, for example, and his sister has been in someone else's house (apparently it would have been rude not to!?!). They will see it as favouritism though. Even after lockdown is over I won't trust that they'll be social distancing and not taking unnecessary risks and I'm just not comfortable with letting them near the baby (equally I don't want to give FIL anything).
I have a difficult relationship with them and they already think I'm an overreactive drama queen (I'm not, and DH agrees with me, they just have weird things like thinking me being picky about child car seats being used properly is being oversensitive - they think seatbelt laws are an infringement of their human rights 
) so this doesn't help either.
WIBU to not let them near the baby until it's safer, when my mum has been able to properly meet and cuddle it? Obviously if rules are relaxed we'll take him/her there while doing social distancing but no holding them.