One day a week is not much. We have DGS1 and DGD sometimes twice a week and now for sleepovers once a month. We also have DGS2 twice a week and 4 times a week if childminder is on holiday. It is tiring and though I am 64 I find it physically exhausting. Also my DM is 85 and increasingly needing help as has advanced macular degeneration. Sometimes I feel overwhelmed and just tired as I am up early when doing childcare - 5.45 for DD1 and 6.45 for DD2. I need paracetamol to start the day as my limbs are so sore. My DH has a brilliant relationship with all DGC but he does the fun things and it is me who does nappies, toilet training, shopping, looking after if ill or hurt themselves, arrange (pre-Covid) things to do - soft play, baby groups etc, arrange (post-Covid) woods, nature trails etc. I could not leave DGS2 who is 2 ½ with him as his expectations of that age are dangerous i.e. he randomly remembers he must go to the garage/upstairs to the computer/upstairs to the loo whilst he is with the DGC and just does it leaving back door open, gate open, toddler at foot of stairs etc. What I am trying to say is I think men are not in tune to the risks of looking after small children and not intuitive to their needs and it is not till they begin to respond that the relationship of grandfather builds. I, DD1 and DD2 also find that DH winds children up at mealtimes and before bed which is difficult to deal with. Sometimes I get on better if he is not there which is a sad thing to say but when our own children were small he was at work and I was at home so maybe understandable. All DGC love their Papa dearly and also the fun they have with him. He did take turns when they were tiny babies with colic but it was me who did the pacing round the garden, singing, rocking for hours on end.
I have age appropriate toys in a box and move anything breakable, damageable as much as possible because it is easier. All the children have responded well to what can/cannot be touched and by 3 are usually reliable to not touch other things although even at 6 can easily get carried away. Personally if I was you I would remove anything breakable or not touchable before the baby came and go out as much as possible. Small children can spend hours digging in mud, throwing stones in ponds and running through grass in woodlands. Get your DD to bring a bag with wellies, puddle suit and all in one. We spend a good ½ hour jumping in puddles, throwing stones, squelching mud - you can't get that time back. My DH I think might have mild ASD maybe why he can't enjoy these things but please don't let it interfere with your enjoyment and relationship with your DGS.