I took my Doberman to a puppy agility class when he finished his kindergarten obedience. He was around 5 or 6 months I think. The jumps he jumped over were the ones set for the toy breeds, basically, sometimes a little higher, but not higher than his elbow. He learned all the names of all the equipment and went on baby bridges, and anything else that could be dangerous.....baby size. He loved going through the tunnel and chute. He ran through, but there was no pressure to hurry or make dreadfully sharp turns. The weave poles were done slowly....just to get some accuracy.
Some people disagree with doing this with young dogs with big bones, but some think it's carried too far.....the paranoia. I checked with my vet first. A beable, I would think would be fine. Check with your vet and take it easy with the agility. It's all about fun anyhow....never ever one negative word. That will ruin their drive later on, when it counts. Hope you can find something. Otherwise, obedience classes are lots of fun or canine good citizen. That's what Lyric is doing right now. Then we're back to agility, I think. Good luck.