I am a preservice teacher, and based on my own personal experiences/observations and what I have learned throughout my coursework, your statement that younger students have a shorter attention span is very accurate. Therefore, how teachers educate older students will be different from the way they educate younger ones.
Firstly, I feel that your current “attention grabber” opening is a great way to begin any lesson. You want your students to get excited about the topic because without this initial excitement, students will not feel motivated to continue on with the lesson. I feel that it is effective to start a lesson by invoking a sense of mystery, so maybe you could hide objects that you are going to be talking about in your hand or under a blanket/bag or you could also start the lesson with a riddle.
Once you are in the “explanation” part of the lesson, incorporate as many games, songs/finger plays, and interactive activities as possible. Many young students are naturally curious and want to be able to move and explore their environment; therefore, try to always think of at least one interactive component in every lesson. For instance, if you were going to teach your students about spiders, you could sing the song The Itsy Bitsy Spider with the accompanying finger play, bring in spider stuffed animals or models for the students to touch and pass around, and make spiders out of food. You could also show them videos and pictures of spiders and make their own spider webs out of string. These ideas were ones that I learned from a workshop that I completed called “Growing Up Wild” that was given by the Maryland Department of Natural Resources.
I also suggest incorporating several brain/stretch breaks. You should preplan these breaks; however, you also need to gauge your students and determine if you may need to initiate the break sooner.
Finally, if you have any students who are particularly antsy, you could give him/her specific classroom jobs, such as passing out materials.
Unfortunately, there is no-one size fits all answer to your question, but I hope some of these suggestions help.