I'd keep it simple. If you're introducing these investors to crypocurrency and you are their primary source of information, then that goes both ways - if their investment takes a hit then you're going to take the blame. Respectfully, it sounds like you have a lot to learn and I'm no expert.
The best thing I think that you could do is buy ETH at whatever amount they want to invest, whether that's before or after they pay you (at your discretion), hold on to it for a week, then sell it to them/set them up with cold storage wallets for 97%. If that were to happen in the very short term I think you'd see a bigger return than the 5%, but that's pure speculation on my part and I encourage you to consider the risks. That might create a tax issue for you - if it does, it's probably best to ask them for a fee. Get clued up on how to safely store ETH, where is good to buy it, sound authoritative and pass the information on, but reiterate that anything can happen and they need to go in with their eyes open.
Going forward, there's money in arbitration between different crypto currencies if you know what you're doing and/or if you're lucky. There can be money in getting in early on new coins that gain popularity. In amongst the noise there are some very clued up people in the forums and there are a few on youtube. Like the real world - buy low, sell high, know when to hold 'em, know when to fold 'em