Those worked well for our son.

you can probably skip the fins if packing is an issue. I had every intention, upon the advice of several parents whose opinion I values, of skipping the fins under the idea that one probably isn't doing hardcore snorkeling that requires the extra power and control fins add.

However, there was no way our son was going without fins. If daddy had fins, he wanted to wear fins!

Our son was 4 yo and we started off the beach. I would think going off the boat would make getting the fins on easier since you won't be battling the sand and him trying to walk in the fins.