We hired a sling from the local sling library for our holiday.
I front carried DS2 at around 22 months (although he was slight) in a toddler connecta.
I basically e-mailed the sling library (I couldn't get there due to work), and said what I wanted to do, and given a choice, we'd like a summer weight sling. The deposit was ££, but returned at the end. It was fantastic, and they posted it to me, and I returned via recorded delivery.
Once on the plane, they were very anti me having him facing me for take off, we had to loosen everything off, and move one leg so they were both on one side of my hips, rather than straddling me.
It was amazing all through the holiday - we didn't take a pushchair, as the location wasn't pushchair friendly (DH's grandmothers, hence no choice!), and I basically carried him for all naps for the 2 weeks. It was hot work!
We even got DS1 (4, and very slight!) in as he felt left out!!!!
Enjoy your holiday.