My wife and I are around 70 years old and would like to get a kayak (or two) that we can use on some of the lake and rivers in SW Michigan.  We are wondering whether a 2-person kayak would be a better choice for us than a single.  We're in relatively good shape.  We'd like to also be able to take a grandchild (around 6 years old) with us on the lake.  We could use some guidance on choosing the right kayak and safety gear we should get.  Thanks.