Should I, for example, ask the buyer to make the payment using his favorite wallet, then copy/paste the transaction id on my website so I can validate it using the blockchain?
No, this is not a great option.
Anyone who knows the seller's address (which includes all your potential customers) can look up that address on the blockchain and see all incoming transactions. A fraudster/scammer could therefore see someone else's payment and claim it as their own. As mentioned above, the only way to resolve a situation like this would be to have the users sign a message from the address to prove ownership.
Signing a message is a special function of bitcoin which uses your private key and a message of your choice to generate an unique signature. Other users can verify this signature, which proves to them you have ownership of the associated address. The issue with using this method is that it is time consuming for both buyer and seller, many buyers may not know how to sign a message, and not all wallets (particularly web wallets and exchanges) have this functionality at all, leaving you caught in limbo.