This is more of a WWYD than AIBU but here goes:
PILs have organised a family party for the bank holiday weekend. DH & I plus our DCs (3y and 9m), SIL, BIL their DD (3m) and BIL's mum as she is visiting from NZ, GMIL who lives very near PILs and GPILs who live miles from anywhere.
MIL asked me and DH if we could pick up the GPILs and bring them. We're happy to do so but it is a 4 hour round trip from our house and then an extra 1.5 hours down to MIL and FIL. We've asked if we can stay on Saturday night at PILS to avoid having to do another 1.5 hours drive later that night. DH and I can both drive but DH is disabled so may not be physically able to share the driving. We're also due to be down near them the next day so we'd have to repeat the journey on the Sunday.
MIL and FIL are fine with us staying, but there isn't room in the house with everyone else so they've said they'd sleep in the caravan. Are we completely UR to take them up on this offer? They're in good health and early 60s if that makes a difference.