Thank you for writing to Alterhéros! You are unsure if you should tell the rest of your football team if you are bisexual because the team president advised you not to.
Unfortunatly you didn't mention how the few people of your team to whom you came out reacted to the news. I think this may be an indicator of the reactions of the rest of your team if you choose to tell them. In any case, you should still reflect on the fact that there might be a few people who will react badly to your sexual orientation. If this happens, it might make you feel uncomfortable when you are with the team, but remember that you can always choose to ignore them. If some of the people end up hating you because of this,they are most likely not people that are worth your time and friendship anyways. There will be others who will respect you for who you are.
A suggestion I have, if you want to see how the team feels about the subject, would be to casually mention one of your friends is bi or gay and see what they answer. It may seem cliché, but it will give you an idea of their stance on bisexuality.
Also, did the team president mention why you shouldn't talk about this? Has he heard homophobic comments from other team members? Asking him might be a good idea.
One way or another, you should do what feels right to you. If telling them is something very important to you, then you should not let your presidents suggestion get in the way. I hope this helps a bit, and please don't hesitate if you have any more questions!