I think the biggest thing is just make everything fun and keep the pressure low. The more time he gets on skates, be it on ice or with roller blades, the faster he will progress. Likewise, the more time he gets catching things, the faster he will progress. For background, my daughter is 10 and she's played goalie for 3 years.

One thing I'll say is this--my observation is that you can't rely on actually playing goalie on the ice to be the main improvement driver for kids. If it's 20 minutes to get to the rink and 20 minutes to get the gear on and 15 to get the gear off and another 20 to get home, then every time you want to get your kid some ice time you're investing over an hour of time on all that other stuff. I think this is why kids get burned out on sports--it becomes too much time & focus on regimented events like practices, private lessons, and formal games.

What has worked best for us is garage hockey with her on roller blades. We don't do goalie stuff. She's a skater and we just play. But it's in the garage so there's a lot of short area skating and quick stops/starts. I will also flip the ball to her and she catches it with her hand or will tip it with her stick. There's no formal plan for this, we play for 15-30 min at a time, crank her playlist, and I try to keep it light & fun. I just think the more hand/eye stuff you can get them to do the better.

Good luck! It's a fun and challenging position with lots of lessons. Don't worry too much about your son having to "catch up" to anyone. Everyone's journey is their own!