We just spend a week with our PIL and the kids had a tonne of screen time. Why? - a combination of needing down time from Xmas excitement and, honestly time away from the PIL who although v interested in their GC are not actually that good with them. Overly controlling, unwilling to be led by them, rigid about wanting to stick to THEIR routines. To get the kids through that, and for me to have some downtime from managing the kids to enable good interactions with the PIL they watched plenty each day.
In day to day life we have time limits and a couple of screen free days each week.
My MIL has expressed her disapproval of the screens. Maybe next time I’ll respond that THEY generate much of the need for them.
We could do screen free visits with PILs if they would fall in with what our family needs and not freak out when the kids play up.
If you want to do something, no don’t say something to the parents.
Do ask the child if they’d like to do something with you. Throw yourself with gusto into whatever they ask. In theory the PIL want to play with our kids. But they won’t be less by their choices so it often doesn’t get off the ground.
We had a very, very similar experience with my PILs, who similarly expressed disapproval of the amount of screen time my son was getting. During their visit he had many hours a day. In day-to-day life he doesn’t get even a fraction of that, but their visit necessitated it - partly because, like your PILs, they really aren’t very good with him (inflexible, put their own wants and needs and routine ahead of his, etc) and partly because of the strain of hosting fairly unhelpful and demanding guests alongside looking after young children.