If you were to choose travel you would have to be well prepared to take the piggies. If you have a C and C, I would use leftover grids, a liner, a piece of cardboard and a towel to create a temporary C and C. Layer the cardboard, towel and liner and create a C and C with grids and connectors. This is my favorite travel/ temporary cage setup. The 1.5 hour drive shouldn’t be too hard on them if you have the right set up. My recommendation is to use a pet store guinea pig cage as these are typically small and not suitable for a permanent habitat they make excellent carriers. However, these are expensive for a carrier and are in the 30-45$ price range. I have found that you can get a lot of use in these for the years to come for vet visits etc. If not there are many acceptable ferret/ Cat If you choose to take the guinea pig with you in the car I would set up the cage with all the essentials hay, bedding or a towel, and a hidey. I would also pack critical care, extra water and hay, your guinea pig first aid kit and criticial care. Because anything could happen. If you want to take the piggies with you ask yourself these questions: Do you have a place to stay that allows pets? Are there other pets there that could be a potential threat to your piggies? Do you have a qualified Veterinarian nearby in case of an emergency? Any pet stores that you can go to with food your piggies like? Access to fresh veggies? Traveling can be very stressful for piggies so make sure that you are prepared for all possibilities.
As for boarding do you have a exotics vet that you go to/ trust? Many vets offer boarding and this a great and safe options for your piggies. Also local guinea pig shelters/ rescues often offer boarding. Perhaps look into a nearby shelter with good ratings, these shelters are well prepared for piggies and boarding here is often affordable and the money goes to a good cause. As for keeping them at a friends make sure the friend is prepared and educated about guinea pigs.
In conclusion, you have many options I recommend looking into to all of them and decidng what is best for you and your pets. Apologies if I rambled on I tend to do that. I think it is very wise and responsible that you are planning ahead. I hope this info helped! Enjoy your new pigs and your holiday and have safe travels! Feel free to follow up if you have further questions!