Proud - you have to make a choice, your mum might be easy childcare for you to use, and if not free, then I would assume cheaper than the going rates, but you do need to think if it works for you. Your mum is not 20-something, 2 toddlers will be exhausting, and she has other children who are allowed to watch TV with her.
There are other things she could have done with your DC, but other things that were harder work for her.
If it is likely you will need regular childcare, then worth finding details of childminders with spaces, or babysitters who are avilable in the day. for weekends, you might find nursery workers or nannies who'll do extra babysitting for a few hours if they can. However, this is not going to be cheap (round here you are looking at between £8 - 11 per hour for qualified childcare).
Really, if you try to push it with your mum, you'll probably hear "no". For most people, a bit of TV isn't a big deal in a home situation and it wasn't a formal childcare setting.
FWIW, my parents have only had DC1 for 2 hours and so far have never had DC2 (similar age to your DC) alone. I wouldn't use them for childcare because I don't think they would look after my DCs very well or in a way I'd be comfortable with, the one time they did have DC1 was more for their benefit and I arrived home to a very upset, overtired baby they wanted to keep awake to play with (vowed not again after that).
My PIL on the other hand, while they feed my DCs food I wouldn't and allow more treats, I don't mind because it's a treat to go to Nanny's house, it doesn't happen often and it's nothing that's a massive deal, a huge pile of biscuits for lunch every day would be an issue if I fed my DCs like that, once a month isn't going to kill them, and they know they don't get that at home, it's a "Nanny's house treat". (Although PIL haven't had DC2 alone in the day yet).
Think about your other childcare options and don't use your mum. Are your PIL local?