Both of my daughters ( now married and away from home ) like the outdoors. When they were young I would take them camping , fishing or just for walks in the woods , later they would take there friends on outings and camping trips. The youngest when she got married , for the honeymoon her and her husband spent a week camping in northern Canada.

One wedding present was a new tent and sleeping bags. ( two of the places for folks to get wedding gifts were Eddie Bauer and L.L.Bean )
The oldest daughter and her husband are into kayaking and outdoor wildlife ( Birds) photography for relaxation
If they help you with the boats , there will be an interest and from there it will escalate into more fun for them since the boat has to be paddled. Then after paddling it , day trips and eventually camping overnight and on to exploring different waterways. Just be forewarned , if they like the boat , they will claim it before you know it.
Been there , did that with the daughters and have two young ladies that enjoy being outdoors , fortunately there husbands also enjoy the outdoors. Lucky for them since it is my guess they would not of had a choice.
Chuck.
PS. The wife's idea of camping is a good hotel with room service and forget about paddling down some river , cruise ships are OK..