The key thing about shielding is whether you had the letter
And then how far you follow the advice
Since 6 July we have been allowed to bubble, including overnight stays, but only with the one person.
Deciding to bubble for a holiday might not be against the rules. Eciaoly as it is one person, and so the bubble is with him/his immediate family only.
That does mean they cannot have indoors contact with another family, but could still see them at minimum 2m distance outdoors
They don't appear to be making a major breach of the current shielding rules, at present.
And yes, the 'bubble with only one other' rule is tough in families where there are eg 2 sets of grandparents, because either they cannot do it at all, or someone ends up feeling miffed.
There is a long thread on shielding families and the return to school. If you dip into that, you might see why those currently shielding (newly deshielded by then) are so very worried about it.
They don't want to do the childcare.
There's a big difference between potential transmission now - when people have been relatively isolated and most socialising is outdoors, and what it will be like come autumn.
If your concern is that your DC is missing her GPS, then perhaps she could see them inside? Or wait a fortnight (with no/low mixing with anyone beyond family) and then go and stay with them before term starts?
The age old question of 'damn, what do do for childcare now that family can't help' is the subject of many threads. You need to start looking for after schooos clubs, a childminder or an afterschool babysitter/nanny. Perhaps teaming up with another family?