AIBU to feel my in-laws could make more effort with our son? Or is this a cultural thing?

It’s your H’s family, so leave almost all of it to him, and do what works for him, you and your DC. Seems like you’re doing ‘wifework’

OP don't invite grandparents who are in their 70s and live an hour away for dinner! Invite them for lunch. You find an hours drive 'difficult' so imagine how they find it. My Mum (unfortunately no longer with us and died at 77) found travelling exhausting in her early 70s. She stopped driving because she found it so stressful having to anticipate what people were going to do (no indicators etc) but that meant negotiating public transport which is not always reliable or forking out for expensive taxis. Oh and she hated driving in the dark. Inviting your PIL for lunch will probably be more acceptable.

But I agree with others, you see them all plenty! We were 4 hours from my parents and saw them roughly every 2 months, and always during the Christmas, Easter and Summer school holidays until the children were teens and didn't want to hang out with 'old people' 😂

Other people having different preferences to yours and having other things to do is not at all sad.

Is it? Seems they have given plenty throughout their life - has this been reciprocated by you and your DH?

Have you heard the expression that children are like farts - your own are just about tolerable and other peoples are grim.

I would concentrate more on the cousins for your only child - that will be the blood relative they will have longest in life. I am really close to my cousins and feel blessed to have them a close friends still now in my 50s.

I think you need to reassess dynamics - why are you looking for childcare, entertainment and hosting from people nearing 80 years of age. It sounds quite entitled and immature of you. Really you should be inviting them to you. Also keep the next generations connected by inviting the SIL and cousin. Do you have siblings and your DC other cousins?

Do you and your husband take them out anywhere with your son during the holidays that you aren't with your parents @singinginthedrizzle ?

Plenty of older people have routines for the weekend, even when retired because that is how it is always been for them so maybe a Sunday expectation is a bit much. My own grandmother is 82 and can't go to church anymore so she watches a service online and then has lunch and does laundry because that was her routine for 60 odd years. She makes an exception for Christmas but that is also a routine (tradition) albeit less established.

You have very involved grandparents. Your expectations are unusual.

Wow. Thats a ‘lot’. I am in a different situation as my husband and I are immigrants so none of this is my life, but I don’t know anyone who sees their parents every other day unless they live together.

Not for them, I guess!

or your husband could initiate more?

I think on average it feels easier for the maternal grandparents (grandmother) than the paternal grandparents (grandfather) because they find it easier to initiate contact with a daughter than daughter in law, and in some families there is the expectation that the calendar of the children is the mother's responsibility, and/or not wanting to be an interfering mother in law.

Once a week/fortnight plus occasional childcare is fine. You're seeing other grandparents once a month as well so that's most weekends taken up.
Do you invite them over for a Sunday lunch? If you want to see more of them I would start there.

Once a week and a full day a month is plenty, probably more than the average UK grandparents, unless they're all out of work or living together.

I think the fact that there are step parents in the mix may also influence things.

You say your husbands stepmum does not have children of her own; maybe that’s not something she wanted, but I would guess that the connection is probably not as strong as if it were a biological grandmother; or she perhaps feels it’s it her place to intrude.

As someone who's lived here for 25 years, it seems plenty to me by modern British standards.
Back home, my family are in and out of each other's houses all the time. Although, my cousin had a baby and I recently found out that they never bring him up to say hello to my granny even though they pass her house every day on their walks. So I had to "tell them off" for that because granny would never ask herself but was desperate to see the baby.
When I moved here, I was told by my partner that you can't just drop off on people and we had to go through complicated arrangement process and strategic diary coordination exercise just to see his parents at the weekend. We also had to call them 20 minutes before our arrival to let them know we were nearly there. And he didn't have a key to the parent's house which was...unusual.. for me.
You have a pretty solid family support from where I stand. And it is quite possible that your IL simply decided they don't want to intrude now you have a child. Most couples I know constantly talk about how they just want to be "just our little family" and so it is no wonder grandparents wait to be invited.

I mean, most people have said it already but yes, they probably think they see you loads already and would be very surprised to hear that you dont feel like its enough!
I imagine that they might also feel like you prefer to do the arranging as you are the one with the children and therefore potentially less flexible than them, they might not want to intrude - maybe you just need to say that? 'Oh btw I know i always ended up arranging us coming over but now the kids are older and things are a bit more settled, feel free to give us a ring to arrange meeting up'

Does your DH's step-mother have children and grandchildren of her own?

When my dad re-married after the death of my mum, they spent loads of time with my step-mother's daughters and grandchildren and pretty no time with me and my children. Even when my children were the only grandchildren before her daughter had children, my dad and step-mother spent all their time with my step-sister and never bothered with my children.

I think it’s a sign of the times, I was looked after by my grandparents most of the week they took it in turns and we always went round for dinner once a week after school, and most weekends there was a roast dinner to be had at someone’s house. We lived 5, and 15 mins away from them. All grandparents were at least semi-retired by the time I was born, and very early at that, one set were aged 46&47 when I was born. I’ll still be doing the school run when I’m 46, my parents are working full time and will be til retirement at at 67. We see our parents birthdays, Easter,Mothers & Father’s Day, Christmas and that’s about it really, they live approx 30 mins away. This is fairly standard for a lot of people I know. There are some who have childcare, my eldests grandparents see them more regularly and often do a pick up and drop off to my ex. They retired early and have more time on their hands. I cannot imagine seeing anyone every other day, that sounds awful.

@NotAnotherScarf being mid/late 70s and not wanting to be around primary aged children or not managing to cook for others isn't prematurely aging yourself, some people are old at that age. Everyone starts to feel that age.
OP do the inviting, but don't put pressure on them, it's sounds as though they are slowing down.

Are there other gc to factor in? Perhaps on the step parents’ sides?

Also, being in their 70s, they may still have their own social life, activities etc. Perhaps commitments to elderly relatives. I know a number of people in their 70s who help to care for elderly parents/aunts/neighbours/friends. Lots of visiting in care homes etc. This may be going on without you really knowing.

Retired people often have a whole range of commitments but they might not talk about them.

You all have regular contact. Your DH could very easily invite his parents/ step parents over for dinner, lunch etc.

Agree! I’d have driven my parents insane if I’d been round every other day with young DS. They had their own lives too, plenty to do. Once a week or so worked perfectly fine for us and DS was close to them.