If experienced and new staff are put together for a training session, how would you manage and deliver the session?

To carry the crowd together the session has to be quite interactive to sustain the interest of new recruits and experienced ones by getting more participation from new recruits and giving opportunity to experienced to share their knowledge and expertise on job in the forum.

This kind of scenario is not so common but it happens once in a while.
For Induction training these kind of situation often arises and gives a little or more hard time for the trainers.
Since the experienced staff knows more basics, the Instructor cannot just rush through the topic because there is new staff also attending training who needs to know/learn more.
Next issue would be when the Instructor do the session much detailed, one could easily say that the senior staff members pays less attention giving signals that these topics are already well aware for them.Class could be easily distracted or deviated in no time.
So, it would be a good idea to take a few minutes to explain these on the beginning of the session so that everybody understand that the session is for all, regardless of the experience and position of the people who are attending the training.
Remember, quality of the training matters more not quantity.

Assuming that we have one experts group and the other are beginners for a certain topic: It is preferable to involve the experienced staff in delivering some training information by asking direct questions, ex.: who can tell us what is the advantage of .....? or what is the difference between....? Moreover, set out group activities and distribute the experienced staff among groups and allow them to monitor and facilitate, yet, present groups activities by the fresh staff.
Thank you Aya for sharing this interesting question, regards.

I should start with why Experienced and New Staff are in the same training session? Unless it is a:
1- Refreshment course/training.

2- New course/training.

3- Other/Special.
Remembering that I am not considering the subject of the course/training (the specialty if it is general or specific material to be delivered), also the trainees experience in what? If it is a Refreshment course/training should be delivered as is, means no experienced or new staff, as the experienced understands it is a refreshment.
The only thing is to make it open to share and transfer experience between them and to make it valuable.
If it is a New course/training, there will be no experienced or new staff, as both are starting at the same level.
If it is a Other/Special course/training it should consider/address the gap between them while it is prepared, which means if the course/training is designed/prepared for experienced you lose the new and if it was designed/prepared for new you lose experienced as they will not focus or give attention as soon as they find that.
Assuming that your query as is, even though it is not precise for the purpose, and assuming that you don't know there is an extreme Experienced & New until you are at the session and knew that at the introductory stage; you should manage yourself as to minimize the gap between them which should take a great efforts to do so, you should be able to adjust your frequency to address both in a way both understands the subject taught.
As an example if I have a course named X and includes a training named XT, and I expect to have both experienced and non-experienced people in both X & XT, the following should be considered: I have to know while I am conducting the interdictory part of the session the experienced and the non-experienced.
Same for the back ground of both as I am in general course X and General training XT, I might have some or none (depending on the number of the people in that course/training) that has a specific background experience in it.
Starting with course I should address some examples tailored for the specific back ground and general for the none specific to make them understand; assuming that the experienced are the specific back ground and the none for the new.
Going through I try to minimize the gap by sharing experience from the different back grounds I have.
Ending with training I appoint groups that mix between specific and none in order to make sure that the specific assist the none.
Knowing that this is my point of view and it extremely varies as it is very general.
If there is specific case it would be better to address.
The combinations to make for the example are many and I intentionally made this to highlight the case.
Hope that I helped in a way or another.
Good luck with your variations.

first of all to have the answer, we have to know the training type & topic of the session