I would say that a lot of what you need you have right with you. We have a lot of new people on our team this year, but it's not that young-dominated.
Here are a few simple ideas:
Let them watch old competition tapes. I am sure you guys ahve them somewhere, but if you don't, talk to archiver site owners. A few teams may have links. Howver, this is an easy way for the younger people to get in touch with what competition is about and they can expect to see.
Get a bunch of new people on your chairman's team. Couple them with older team members and try and produce ideas and brainstorm. Not only are you getting some great work done, but you're giving them room to think for themselves about the team values. Do the same thing with Tech also.
Do a presentation on team history. Maybe get up in front of the team every day and tell a fun fact, like "in 2002 our team won the chairman's award at...". Also, it's a good time to teach them how to talk to judges and stuff like that, and what to say. Everyone on your team shoudl be able to.
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A really important aspect of inspiration is personal communication. Try to get to know all these new members. If they make connections with upperclassmen and mentors now, they'll be really eager to come back again. I would recommend hosting a student forum, students only, so that the younger and possibly more shy teammates can express themselves. It's a good way for people to bond, and for things to stay open.
Good luck!
- Genia