Wallsendgran, crikey! - are you overthinking this! You really don't need to be an expert, or even have up-to-date knowledge.
Everyone is contactable, on the phone or with a text. You won't be all alone. Have they even asked you to babysit?
My daughters both had over a year off on maternity leave and breast fed. One is very relaxed and quite happy for me to just do my usual thing. The other has a very strict routine of sleep times, vegan foods, no sugar, only water to drink, no TV, baby-led weaning etc. so I'd always ask or check, if in any doubt! (I gave her three-year-old a vegan sweet, as his cousin was eating them, to be told off - he'd never had a sweet in his life, poor thing.)