I call BS my friend. You're not plowing new ground here Scott - we've all had to go through it. You admitted - YOU are anxious - just do it... cut the cord... there is no "sign" alerting you that "older kiddo is ready." Or, just let them cling to mom and you can bet those behaviors will become habituated and you'll struggle to get that little trail partner for the rest of their lives. I know. I had one that would rather have been with mom as a nipper but once she got outdoors with dad... it was fun. Now she's 26 and on her own, but she still likes to go out with dad. I can supply testimonials from forum members if you desire.
Once your little one gets out in nature with dad and you share your time and explore the simplest, tiny wonders that nature has to offer with them, that separation anxiety will melt away beau coup quick. That little stream to splash in, that fallen tree to climb on, that tide pool to observe the ocean's tiniest creatures, the littlest things nature has to offer is a wonderful world of excitement for the young curious mind.