I have to add from the other side here... I had booked a holiday before I split with their father. My Mum offered to come instead.
We went abroad June 2014, DS was 23 months and DD 4years6months ish. I didn't have good control of the kids then so it was hard but at yours age it might be easier. Mum sometimes went to do her own thing and my worst memory is at the pool (the kids pool was next to the adult pool). Both were playing at the kids pool with me, DD slipped so I grabbed and steadied her and in the split-second I let go of DS and then turned back round to him, he had taken off and I couldn't see him anywhere, once I spotted him he was running towards the adult pool. He got onto the steps and nearly under the water before the lifeguard grabbed him - thank god he was paying attention. A couple of other things - losing one at the packed mini disco because they both came back to the table in different directions, difficult to get all 3 of us in toilet cubicles at the zoo etc. then DD had a sore tummy and was up for a couple of nights and we had to stay in the room, DS was climbing the walls needing out to play but also because we were all in the same room he was always woken by DDs crying too! I always said I would never do it again. Both were so exhausted from the travelling we were also carrying one each sleeping child each at airport onto the bus to hotel - I absolutely couldn't have carried a sleeping child and held luggage and held onto the other child too. :O I took a buggy and reins but they take the buggy away on boarding and you dont' get it back to the luggage carousel.
It's very different with one child to watch than 2, I would take a single child anywhere but it's very hard to take 2 on your own! I would also take a baby anywhere with a child as you can always have the baby on you but theres just something about trying to keep constant hold of young children who don't understand danger at all and just run off in opposite directions. I will say that my kids were pretty "wild" I'm not sure if all kids are like that in their toddler years, my 4.5 year old is still unpredictable at times but my 6 year old is calm and trustworthy now.
We do have some fantastic memories though. I always said never again but I am going to next Summer when DS will be 6 and DD 7.5.
Do you have a friend who would be willing to come to help if you paid their place?